Light Metals 2019

BauxiteBauxite is the major aluminaAlumina (Al2O3Al ) bearing ore used in the aluminumAluminum manufacturing industries. The bauxiteBauxite containing less than 50% AlAl 2O3 is called low-grade bauxiteBauxite ore which is commonly used for the aluminaAlumina -based abrasives and refractoriesRefractories productions. The aluminaAlumina -silica and aluminaAlumina -ferrite complexes are the foremost impurities present in the low-grade bauxiteBauxite . They affect its commercial utilities due to development of poor binding property in the aluminaAlumina grains, which creates mechano-physical problems. Therefore, they must be removed from the low-grade bauxiteBauxite . Different conventional bauxiteBauxite purification or beneficiationBeneficiation methods have been used for their removal; however, they have several limitations. Bio-beneficiationBio-beneficiation is a potential solution to the problems associated with conventional methods. In the bio-beneficiationBio-beneficiation process, the biological agents such as microorganisms and their metabolic products can mobilize or polarize different impurities present in the low-grade bauxiteBauxite by means of the active redox environmentEnvironment created by them in the indigenous atmosphere. Many reports have suggested that Paenibacillus polymyxa efficiently removes calcium from the low-grade bauxiteBauxite . Similarly, iron-oxidizing and silicateSilicate bacteriaBacteria remove iron and solubilise silica, respectively, from the low-grade bauxiteBauxite . However, pilot scale operation of the bauxiteBauxite bio-beneficiationBio-beneficiation process has not been reported. Research related to biotechnologyBiotechnology should be undertaken in the future to develop a comprehensive and efficient process for the bio-beneficiationBio-beneficiation of low-grade bauxiteBauxite ore.

Thermal activationThermal activation of bauxiteBauxite has been proposed to enable removal of organic carbon and reducing boehmite digestion temperature. However, there is limited published research about how thermally activated bauxiteBauxite behaves at pre-desilicationDesilication (<100 °C) conditions. Combining x-ray diffractionX-ray diffraction and scanning electron microscopy energyEnergy dispersive spectroscopy analysis of cross-sectioned samples, key differences in the desilicationDesilication of bauxiteBauxite and thermally activated bauxiteBauxite are identified. The results show that the silicateSilicate dissolutionDissolution rate of activated bauxiteBauxite is fast and desilicated products do not appear within the first half an hour. At the same time and temperature, the leaching rate of aluminiumAluminium bearing phases is inhibited by thermal activationThermal activation . The subsequent filtrationFiltration rate for activated bauxite residueBauxite residue is significantly shorter than for bauxite residueBauxite residue . EnergyEnergy dispersive elemental mapping indicated thermal activationThermal activation enables the dis-association of kaolinite phases from hematite and inert aluminaAlumina phases.

Dewatering and transporting slurries are two common challenges aluminaAlumina refineries face today. AluminaAlumina Refineries are seeing lower available aluminaAlumina and increased gangue minerals which makes handling of red mudRed mud more difficult. While polymers are necessary to achieve faster rates of liquid-solid separation, they can impart negative rheological characteristics, so polymers alone in most cases are not sufficient in the washing of red mudRed mud that contains higher gangue minerals and lower available aluminaAlumina content. Solenis’ rheology modifiers have been successful in bench-top testing, pilot and plant trials at improving rheological characteristics, liquid-solid separation and washing efficiency (savings of caustic and aluminaAlumina by efficient washing of red mudRed mud ) within the counter current decanter circuits of aluminaAlumina refineries. This paper will cover the efficacy of the rheology modifiers that have been successfully demonstrated from bench-top experiments to full plant trials as a viable solution for rheology modificationModification improvement in the aluminaAlumina industry.

RefractoriesRefractories are key components for the productivity of a calcination unit. Unexpected halts caused by refractory failures directly affect the production plan and lead to considerable financial losses (lost income, additional material purchasing and installation). In parallel, planned overhauls are relatively longer due to the time associated with equipment cooling down, inspection, descaling, applicationApplication of new linings and dry-out process. Typically, the overhaul time ranges from 12 to 40 days, reaching volumes of 250 ton of installed refractory and with costs in the order of US$ 1.5–3 million. Due to the importance of refractory working lifeWorking life , there is a need to develop a systemic approach that considers data from laboratoryLaboratory , plant trial and large-scale implementation studies in order to extend working lifeWorking life and deliver cost savings. This paper will present various examples of materials replacement in critical areas of the calciner, and the attained performancePerformance during operations.

The existence of sulfurSulfur and silica in bauxiteBauxite influence the product quality of Bayer aluminaAlumina . The synchronous desulfurizationDesulfurization and desilicationDesilication of low-grade and high-sulfurSulfur bauxiteBauxite through reverse flotationReverse flotation processes were studied using modified starch as depressants in this work. The effects of depressant dosage, modified depressant dosage and collector dosage on flotation performancePerformance were investigated. The results show that the sulfurSulfur and silica in bauxiteBauxite were successfully decreased through the reverse flotationReverse flotation . With an optimal condition of 10% solid density, particle sizeParticle Size of −74 µm of 75%, pulp pH 9, temperature 30 °C, modified depressant dosage of 50 g/t, copperCopper sulfate dosage of 20 g/t, combined collector dosage of 220 g/t, and terpenic oil dosage of 120 g/t, the recoveryRecovery of AlAl 2O3 reached to 76.41%. The sulfurSulfur content of concentrate was decreased from 2.87 to 0.27%, with an aluminumAluminum to siliconSilicon ratio (A/S) increasing from 3.36 to 8.09.

Coal fly ash (CFA) is a solid waste from burning coal in power plants and has caused serious environmental problems. From this study, a three-staged process: sulphating-roasting, leaching and electrolysis, to produce aluminaAlumina from coal fly ash in an environmentally-friendly manner is proposed. In this work, the key process of electrolysis was investigated in detail, batch experiments were performed to evaluate the potential effects of important parameters such as electrode distance. The electrolytic products were analyzed by XRDXRD , XRFX-ray fluorescence (XRF) , SEM and Particle sizeParticle Size distribution (PSD). The results showed that the electrolysis products were AlAl (OH)3 which can be used for aluminum reductionAluminum reduction . Moreover, the electrolysis mechanisms in sulfuric acid leachate are also discussed.

Optimizing bauxite residueBauxite residue disposal is a goal for most aluminaAlumina refineries. Cost reductionCost reduction , increased disposal area lifetime, and a more sustainable operation are some of the targeted objectives. In light of these objectives, the adoption of a dry disposal system using filter pressFilter press has become a very reliable solution in the last few years. However, there are different options to apply this system in plants that already has drum filters: replacing the existing ones or combine new and existing filters. CBA’s (Companhia Brasileira de Alumínio) aluminaAlumina refinery designed a system with two stages of filtrationFiltration (using existing drum filters and installing new filters press) to dispose bauxite residueBauxite residue into the operational disposal area. This paper describes the methodologyMethodology , pilot tests and operations of the filter pressFilter press installed in the plant.

Since 2006, Alteo Gardanne AluminaAlumina Refinery has launched a significant environmental program to improve its management of bauxite residueBauxite residue as well as wastewater disposal. Red mudRed mud from bauxite residueBauxite residue had been sent to the ‘Fosse de Cassidaigne’, a trenchTrench in the Mediterranean Sea via a 55 km long pipe, for 50 years. Due to ever improving environmental standards and the need to adhere to new regulationsRegulations , Alteo rethought its methodologyMethodology by implementing 3 major operational changes: Red mudRed mud bauxite residueBauxite residue dehydration with press filters (from 2006) in order to directly stack the residue in a small dedicated area, 4 km away from the refinery Suspended solid elimination in wastewater still discharged to the sea with pressure filter technologyTechnology (since 2016) Waste water pH reduction and dissolved metal removal, in particular aluminumAluminum and arsenic, by CO2 neutralization process (planned for 2019) with precipitated solid recyclingRecycling in the Bayer process. Further improvements are already under investigation, and will be presented as a conclusion of this environmental friendly transformation of the first and oldest aluminaAlumina refinery in the world.

Biological neutralisation of pH, driven by the microbial fermentation of added organic carbon substrates such as glucose, has recently emerged as a promising technique for remediation of bauxite residueBauxite residue , dropping pH from >11 to <8 in five days. Here, we report on a glasshouse experiment combining this novel microbially-driven pH neutralisation technologyTechnology with other existing (abiotic) remediation approaches, including addition of gypsum, sewage sludgeSludge , and irrigation. ScalingScaling up the bioremediation treatment by three orders of magnitude from previous laboratoryLaboratory trials to these glasshouse trials was successful. Adding bioremediated residue (5 cm thick) at the residue surface significantly enhanced pH neutralisation to depth, decreasing pH from 13 to ~10 as far as 25 cm below the residue surface. Increasing irrigation and tillageTillage frequencyFrequency accelerated salt removal. Combining our microbial bioneutralisationBioneutralisation treatment with fortnightly tillageTillage and daily irrigation provided the best opportunity to rapidly decrease pH and salinitySalinity , and is currently being trialled at field scale.

To solve the problem of high alkali red mudRed mud stockpiling, a new method of “calcification and carbonization” to treat Bayer red mudRed mud was proposed. The carbonization process of calcified slag in the process was mainly studied in this paper, that is, the hydrogarnet in the calcified slag was decomposed by CO2 at high temperature and high pressureHigh pressure . Firstly, the water model experimentsWater model experiments were conducted under different ventilation modes to investigate the influence of pressure on the bubble disintegration and dispersionBubble disintegration and dispersion in the 1 L high pressureHigh pressure transparent autoclaveTransparent autoclave . The results showed that the number of bubbles was less, and the mean diameter was smaller under the airtight conditions whereas the number of bubbles was more, and the effects of gas bubble disintegration and gas liquid mixing were better under the circulated condition, which was beneficial to the mass transfer and the chemical reaction rate between gas and liquid. Secondly, the influence of these factors on the carbonization process of calcified slag was verified in the 2 L high temperature and pressure reactor. The optimum experimentalExperimental conditions were obtained by measuring the carbon content of the slag in the reaction process. The results showed that the reaction time under the circulated condition was reduced by 23% compared with airtight conditions.

BauxiteBauxite residues can pose an environmental risk mainly because of their alkaline nature and the presence of trace elements. Phytostabilization seems to be a promising rehabilitation option and physicochemical assessment remains the primary indicatorIndicator of rehabilitation success. To further understand the potential for rehabilitated residues to support both vegetation and soil faunal communities, a series of ex situ exposure tests was conducted. Plant germination, seedling development and trace element uptake were assessed using the Phytotoxkit™ approach. Avoidance and survival tests soil faunal species Eisenia foetida, Folsomia candida and Allobophora chlorotica were conducted to determine possibility of inhibition in residue soils. Unamended residue is inhibitory to plant growth and mesofaunal establishment. Amendment improves the physicochemical properties of the residue, and data revealed that both gypsum and organic addition is required to promote conditions favourable to plant growth and mesofauna establishment.

Over 100 million tonnes of bauxite residueBauxite residue is produced annually as a by-product of the Bayer process. Bauxite residueBauxite residue utilisation represents both a challenge and an opportunity for the aluminaAlumina industry. Bauxite residueBauxite residue is a fine-grained, complex mixture of numerous mineral phases, which varies based on refinery operating conditions and bauxiteBauxite ore. Quantitative X-ray diffractionX-ray diffraction by Rietveld refinement was used to characterise several industrially sourced residues and better understand the potential value and risk in this material. Particular emphasis was placed on characterisation of aluminiumAluminium bearing phases to identify opportunities for process optimisation and residue utilisation. Analysis revealed that a significant proportion, up to 66%, of the total aluminiumAluminium in some residues can be hosted within iron oxides via solid solution.

For moving towards a sustainable future and building the circular economyCircular economy , there is a push towards waste valorizationWaste valorization . Bauxite residueBauxite residue is the by-product of the Bayar process for aluminaAlumina production. It contains considerable amounts of rare earth elementsRare earth elements (REEs) and refractory metalsRefractory metals , some of which are considered critical materials and initiatives have begun to mine them from secondary sources, such as landfilled industrial process residues. Here, we develop a novel pyro-hydrometallurgical process called acid-baking water-leaching to extract REEs and refractory metalsRefractory metals from bauxite residueBauxite residue . In this process, bauxite residueBauxite residue is mixed with concentrated sulfuric acid, baked at 200–400 °C, and leached in water at ambient conditions. Compared with conventional hydrometallurgical processes, the developed process offers the advantages of less acid consumption, less wastewater generation, and fast kinetics. Work is currently underway to develop this promising technique as the first step of a potential near-zero-waste integrated process for the sustainable valorization of bauxite residueBauxite residue .

Bauxite residueBauxite residue (red mudRed mud ) is a hazardous wasteHazardous waste generated from aluminaAlumina refining industries. Bauxite residueBauxite residue contains elevated concentrations of several elements, such as iron, aluminumAluminum , titanium and sodium. Due to the high concentration of sodium, the bauxite residueBauxite residue cannot be directly employed as a raw materialRaw material for iron-making. In this work, the migrationMigration of iron, aluminumAluminum and alkali metal within a pre-reduced-smelting separationSmelting separation was investigated. The results showed that the content of iron, AlAl 2O3 and Na2O in pig iron and slag are 94.07, 0.11% and 0.013, 9.23, 48.63 and 4.92%, respectively; effectively separating iron into the pig iron and aluminumAluminum and sodium into the slag. The obtained pig iron can be used as the burden for an electric arc furnaceElectric Arc Furnace (EAF). Meanwhile, the slag can be leached by alkali leaching to extract aluminumAluminum and sodium.

Coating of AlAl on various materials contributes to increase the widespread use of AlAl and AlAl coated materials in various industrial applications. There are several methods applied for AlAl coating such as hot dipping, thermal spray, chemical vapor deposition, physical vapor deposition and electroplating. Low-temperature electroplating process is the most economical method. In this research, AlCl3/dimethyl sulfone has been proposed for electroplating at low temperature. Furthermore, the effect of amine additives on the thickness, stability and the purity of the deposited film were investigated. These amine group additives bring the change in the surface morphologyMorphology and crystal orientation of the AlAl film. Preferential adsorption of amine groups on the surface of the aluminumAluminum film lead to reduction of Cl and S and consequently decrease the cracksCracks from aluminumAluminum film surface.

AlAl -Fe-V-Si and AlAl -Fe-Cr-Si quaternary alloys were produced by arc meltingMelting and chill castingCasting , and the crystal structures of the $$ \upalpha $$ -phase intermetallicsIntermetallics (Pm-3 or Im-3, a = 1.25–1.27 nm) that formed are compared with those in the well-characterized AlAl -Mn-Si and AlAl -Fe-Mn-Si systems produced by arc meltingMelting . The crystal structures were refined using synchrotron x-ray powder diffractionPowder diffraction , and compositions were determined using electron probe microanalysis (EPMA). It was shown that the AlAl -Fe-Cr-Si, AlAl -Fe-V-Si, and AlAl -Fe-Mn-Si systems appear to have the same $$ \upalpha $$ -phase structures after heat treatment at 500 °C. Additionally, a new $$ \upalpha $$ -phase with low Si content was observed in the AlAl -Fe-V-Si alloys in the as-cast condition.

Reinforcement kind and ratios have significant effects on the metal matrix composite (MMC) materials. In this study, two different (B4C and SiC) reinforcement compounds between 5 and 15 wt% reinforcement ratios were used in AlAl -Si main matrix composite materials. Samples were produced via powder metallurgyPowder Metallurgy (PM) method and were subjected to metallographic investigation with; SEM, EDS, FASTMAP, Optical Microscope analyzing methods. Microvickers measurementsMeasurements were carried out as HV1 load. The effects of B4C and SiC reinforcement in MMC were compared in details with these investigations.

AluminiumAluminium based alloyAlloy provides good combination of strengthStrength and corrosion resistance. They are light in weight, economically viable, amenable for production by various processingProcessing techniques and possess high strengthHigh strength . AluminumAluminum and its alloys have been a successful metal material used for many applications like commodity roles, automotive and vital structural components in aircrafts. The present research was aimed at studying the effect of manganeseManganese (Mn) addition and laser parametersLaser Parameters on the morphologyMorphology and distribution of the iron-containing intermetallicsIron-containing intermetallics in the AlAl -Si-Fe-Mn coatings. These Fe-intermetallic compounds influence the material properties during rapid cooling by laser deposition technique and play a crucial role for the material quality. Thus, the necessity of the effects of manganeseManganese addition on the surface properties of AlAl -Si-Fe-Mn alloyAlloy . A 3 kW continuous wave ytterbium laser system (YLS) attached to a KUKA robot which controls the movement of the alloying process was utilized for the fabrication of the coatings at optimum laser parametersLaser Parameters . The fabricated coatings were investigated for its hardnessHardness performancePerformance . The field emission scanning electron microscopeScanning Electron Microscope equipped with energyEnergy dispersive spectroscopy (SEM/EDS) were used to study the morphologyMorphology of the fabricated coatings and X-ray diffractometer (XRDXRD ) for the identification of the phases present in the coatings. The refined microstructures and enhanced hardnessHardness performancePerformance were attributed to metastable intermetallic compounds, addition of manganeseManganese and optimizedOptimized laser parametersLaser Parameters .

Increased demand for light-weighting in passenger vehicles has created a need for strong, light, ductile materials to be used in body-in-white applications. The AA6xxx-series of aluminum alloys are suitable candidates meeting most requirements but can fall short of the formabilityFormability demands of designers, necessitating an understanding of what controls the formabilityFormability in this alloy series. This work examines the effect of copper alloying in AA6xxx on the pre-ageing and natural ageingNatural ageing responses of the microstructure and mechanical propertiesMechanical properties . The changes in microstructure observed by differential scanning calorimetry and hardnessHardness testing are related to the work-hardeningWork-hardening and strain-rate sensitivityStrain-rate sensitivity parameters for these alloys measured by tensile testing. An observed asymmetry in the measured strain-rate sensitivityStrain-rate sensitivity associated with increasing versus decreasing strain rate changes suggests that a different mechanismMechanism operates for the two conditions. It is postulated how this asymmetry in strain-rate sensitivityStrain-rate sensitivity will impact the necking and ductilityDuctility behaviour of these alloys.

In this study, metal matrix composite (MMC) materials were produced via powder metallurgyPowder Metallurgy (PM) technologyTechnology . Main matrix was obtained with AA2196 (AlAl -Li AlloyAlloy ) and TiB2 was used as reinforcement materials. In study; TiB2 reinforcements ratio were chosen between 5 and 15%wt. The metallographic investigation was realized with; SEM, EDS, FASTMAP, Optical Microscope analyzing techniques. HardnessHardness values were obtained with HV1. In the study, the reinforcements could be distributed in main matrix homogeneously, via PM technique. The MMCsMMCs hardnessHardness values increased with the edition of TiB2 reinforcement.

The kinetics of retrogressionRetrogression in a high-strengthStrength aluminumAluminum AA6013-T6 (AlAl -Mg-Cu-Si) sheet are investigated to determine retrogression heat treatmentsRetrogression heat treatments that allow subsequent reaging to approximately peak-aged hardnessHardness and strengthStrength . The goal is to combine retrogressionRetrogression with simultaneous warm forming of AA6013-T6 sheet. This new approach is termed retrogressionRetrogression forming. Differential scanning calorimetryDifferential scanning calorimetry is used to measure the activation energyEnergy of retrogressionRetrogression in AA6013-T6, which was determined to be 160 ± 30 kJ/mol. Heat treating experiments determine the change in hardnessHardness during retrogressionRetrogression as a function of time for temperatures ranging from 230 to 250 °C. The concept of temperature-compensated time is used to predict retrogressionRetrogression times and temperatures that allow for the recoveryRecovery of nearly peak-aged strengthStrength through a subsequent reaging treatment. Different reaging heat treatmentsReaging heat treatments are investigated for recovering the hardnessHardness lost during retrogressionRetrogression .

The demand for lightweight and fatigue-resistant solutions in the automotive and aerospace industries requires the extensive use of light metals like AlAl -Si-Mg aluminumAluminum cast alloys. To ensure a safe design for fatigue-loaded aluminumAluminum cast components, the relation between microstructureMicrostructure characteristics of α-AlAl dendrites (e.g. dendriteDendrite arm spacing, microhardnessHardness ) and interdendritic AlAl -Si eutecticSi eutectic (e.g. Si eutecticSi eutectic morphologyMorphology ), stress-strain behaviorStress-strain behavior and fatigue lifetime including the number of cycles to crack initiation and crack propagationPropagation behavior has to be understood. For this purpose, fatigue tests in the LCF and HCF regime from 1E2 to 1E7 cycles were performed for aluminum cast alloyAluminum cast alloy EN AC-AlSi7Mg0.3. With this, the effect of α-AlAl microhardnessHardness and Si eutecticSi eutectic morphologyMorphology was investigated on monotonic and cyclic stress-strain behaviorCyclic stress-strain behavior by performing tensileTensile , incremental step (IST) and constant amplitudeAmplitude tests (CAT) in the LCF regime. Moreover, microstructureMicrostructure -specific S-N curves were determined in the HCF regime until 1E7 using online hysteresis analysis and alternating current potential dropAlternating current potential drop (ACPD) method for monitoring the deformation and damage evolution. Hereby, computed tomographyComputed tomography (CT) analyses were used to evaluate the damage state intermittent and post-mortem in CAT. As a result, ACPD method could be validated as a sensitive and reliable technique for quantitative characterizationCharacterization of stress- and cycle-dependent deformation and damage behavior including cyclic hardening, softening and saturation as well as crack initiation and propagationPropagation until failure.

The microstructureMicrostructure of different hypereutectic Al-Si alloyHypereutectic Al-Si alloy prepared by high pressureHigh pressure die castingDie casting (HPDC), including pores, primary silicon particlesSilicon particles (PSPs) and Cu-rich phases was characterized using synchrotron X-ray tomographyX-ray tomography . With the microstructureMicrostructure distribution, the tensileTensile crack surfaces were analyzed based on the laboratoryLaboratory CT reconstruction techniques, without which previous mechanical failure analysis was hard to conduct due to the low elongation of such alloyAlloy . The fractography feature agreed well with the microstructureMicrostructure feature and revealed the crack extension route during fast fractureFracture . Besides, such technique provided a new method for analyses of other mechanical failure such as fatigue and reconstructed fractography and SEM observation offered new quantitative analyses of crack propagationPropagation . Generally, the existence of PSPs in the hypereutectic Al-Si alloyHypereutectic Al-Si alloy had an effect on the mechanical performancePerformance by influencing the crack propagationPropagation route no matter in tensileTensile crack and fatigue failure.

Combining the retrogressionRetrogression heat treatment with simultaneous warm forming provides an opportunity to significantly increase the formabilityFormability of high-strengthStrength aluminum alloysAluminum alloys while subsequently regaining peak-aged strengthStrength through a single reaging heat treatment. This new technological approach is termed retrogressionRetrogression forming. Forming conditions suitable to the retrogressionRetrogression forming of an AA7075-T6 sheet material are examined through elevated-temperature tensileTensile tests. Temperatures from 180 to 220 °C are investigated. Strain rate sensitivity and reduction in area increase with increasing temperature. Elongation to rupture increases with decreasing strain rate. An elongation to rupture of 35% was measured at 200 °C for a true strain rate of 3.2 × 10−3 s−1. While higher temperatures and slower forming rates encourage the behaviors associated with good formabilityFormability , these must be balanced with the ability to reage to high strengthHigh strength after forming. Recommendations for designing and implementing retrogressionRetrogression forming of AA7075-T6 sheet are presented.

Great attention has been focused on the design of good thermal conductivityThermal conductivity and high strengthen AlAl -Si alloys to ensure that the electronic components can withstand loads and dissipate heat. Herein we report a high performancePerformance Al-Si alloyAl-Si alloy with a thermal conductivityThermal conductivity of 169.34 W/m K. The prominent performancePerformance is due to the systematic optimizationOptimization of micro-structure controlling-that is, reducing the solute elements in the primary phase and controlling the size, morphologyMorphology and distribution of the siliconSilicon phase particles. By these means decreased the scattering rate of free electrons and increased the mean path of free electrons in the alloyAlloy .

The design of materials through the selection of the chemical composition, thermodynamic modelling, melt treatment, correctly developed casting Casting technology Technology followed by adequate heat treatment could improve casting Casting properties. A wide range of complex reactions and intermetallic phases occurs due to numerous alloying (Si, Mg, Cu) and trace elements (Fe, Mn) interaction. Determination of solidification Solidification sequence was performed by modeling Modeling of equilibrium phase diagram, simultaneous thermal analysisThermal analysis and metallographic investigations. Microstructure Microstructure revealed needle-like Al Al 5SiFe and Chinese script phase Al Al 15(Fe,Mn,Cu)3Si2 enriched in copper Copper . Copper Copper addition resulted in formation of compact complex intermetallic phases Al Al 5Cu2Mg8Si6 and Al Al 8FeMg3Si6. Solidification Solidification ended with secondary eutectic Eutectic phases Mg2Si and Al Al 2Cu. Wide spectra of favourable intermetallic phases comprehend to the tensile Tensile mechanical properties development already in as-cast state. Comparison of yield and tensile strength Tensile strength with commonly used AlSi7Mg alloy Alloy indicates significant increase of investigated properties for innovative chemistry of AlSi7Mg(Cu) alloy Alloy in as-cast state.

Open cellOpen Cell metallic foams are versatile materials that have various applications in engineering and technology due to their unique properties. Especially, aluminum foams are getting more attention because of their superior mechanical propertiesMechanical properties . In this study, open-cell aluminum foams with pore sizes of 25 and 40 ppi are produced via polymer replication methodReplication Method . 6063 series aluminum alloyAluminum alloy is used to produce open cellOpen Cell foam and polyurethane foams are used as a model material. Induction sinteringInduction Sintering is chosen to shorten long sinteringSintering time and make aluminum foamAluminum Foam production industrially applicable. SEMScanning Electron Microscope (SEM) , EDS, and XRD analyses are applied in order to investigate the morphology, chemical components and phases of the aluminum foams. There is no carbon peak observed in XRD analysis. The mechanical propertiesMechanical properties are measured by microhardness tests. Vickers HardnessHardness of the samples are measured as 29.9 ± 3.2 and 32.4 ± 2.7 for A1 and A2 samples, respectively.

This paper deals with the investigation of the thermomechanical processingProcessing of AA5083 Aluminium alloyAluminium alloy sheet of thickness 3 mm to develop a fine-grained structure sheet for automobile body structure and general engineering structure. The as-received 3 mm sheet was rolled in hot and cold conditions. In hot and cold rollingHot and Cold Rolling , 3 mm sheet was subjected to reduction in thickness to 1.57 mm. The proof stress, ultimate tensile stressTensile Test and % elongation was found out. The non-linear plastic region clearly depicted that true stress increased with true strain. This clearly indicated strain hardening behavior with a coefficient (n) 0.18–0.11. At lower % of the reduction, the coefficient of friction (µ) was in the range 0.06–0.09, and at higher, µ is increased to 0.11–0.15. Electron backscattered diffraction analysis was carried out to study the microscopic grain orientation. The aspect ratio of the cold-deformed grains is high as compared to hot rolled samples.

The tensileTensile behavior of high vacuum die-cast AlSiMgMn alloysAlSiMgMn alloys at as-cast and T6 heat-treated conditions was investigated with in situ SEMIn situ SEM . For the alloys at both conditions, the cracksCracks initiated from small subsurface gas pores with several microns. For the as-cast alloysAs-cast alloys , slip bands and plastic deformation were obvious in the α-AlAl grains. The cracksCracks expanded rapidly within the eutectics. After the T6 heat-treatment, the eutecticEutectic regions were separated by α-AlAl grains and the eutecticEutectic Si particles became globular shape. Hence the elongation improved significantly but the UTS decreased due to decrease of eutecticEutectic fractions. The crack grew with connecting the voids between the aluminumAluminum matrix and particles. The α-Fe intermetallicsIntermetallics in as-cast status were prone to cause microcracks. Though the shape of intermetallicsIntermetallics was hardly changed by the T6 treatment, the denency of microcrack formation on them decreased.

The present work deals with effect of strontium and manganeseManganese on modificationModification of iron intermetallicsIron Intermetallics in recycled aluminium-siliconAluminium-Silicon alloysAlloy . AlAl -Si alloys with the addition of 1 and 2% Fe were prepared using casting methodCasting method . In order to modify the brittle intermetallicsIntermetallics , Sr and Mn were added to AlAl -Si alloys. Result shows that manganeseManganese modifies β-AlAl 5FeSi compounds by transforming the needle-like structure to a script-like morphologyMorphology . Increasing Mn content to above 0.5 wt%. resulted in the formation of large chunks of α-phase compounds. Most of these large chunks were identified as α-AlAl 15(Fe,Mn)3Si2. Further, the addition of strontium showed only a little modificationModification of iron intermetallicsIron Intermetallics , but it modifies silicon particlesSilicon particles present in AlAl -Si alloys, refining their needle-shaped structures. This morphological transformations may be helpful in improvement of tensile propertiesTensile properties of the modified AlAl -7Si cast alloys compared to the unmodified AlAl -7Si cast alloys.

The effect of holdingHolding time and temperature in the Modified Strain Induced Melt Activation process on microstructureMicrostructure and mechanical properties of AlAl -7 wt% Si alloyAlloy was investigated. AlAl -7 wt% Si alloyAlloy was prepared through meltingMelting and castingCasting route. The alloyAlloy was homogenized at 540 ℃ for 6 h. The plate was deformed 40 and 60% by warm rolling followed by air cooling. The deformed samples were heat treated for different temp. (585, 595 and 605 ℃) and time (10, 30 and 60 min). The microstructureMicrostructure and mechanical properties of Modified SIMAModified SIMA treated samples were evaluated and compared with as-cast samples. It is observed that with increasing isothermalIsothermal holdingHolding temperature and time during Modified SIMAModified SIMA process, the mechanical properties such as yield strengthStrength , ultimate tensile strengthTensile strength and hardnessHardness are increased but percentage of elongation decreased. The better combination of mechanical properties was obtained when 60% deformed alloyAlloy was isothermally hold at temperature 585 ℃ for 30 min.

Al-Si foundry alloysAl-Si foundry alloys are widely used in aerospace and automobile industries, such as the engine blocks and cylinder heads. These engine components are often exposed to cyclic mechanical stress at high operation temperature (250–350 ℃) and such dynamic loading frequently results in the occurrence of fatigue failure. Hence, a fully understanding of fatigue behaviors at elevated temperatureElevated temperature of Al-Si foundry alloysAl-Si foundry alloys is the critical concern for safetySafety designs. In the present study, two typical Al-Si foundry alloysAl-Si foundry alloys , namely 356-T7 and 319-T7, were investigated to discover their low cycle fatigue (LCF) behavior at 300 ℃. The LCF tests were performed in the strain-controlled compression-tension mode with the strain ratio of Rε = −1 at various strain amplitudes of 0.1–0.6%. The cyclic strain-stress response, hysteresis loopsHysteresis loops and the Masing behavior were analyzed and compared between two alloys. Fatigue parameters were calculated from experimentalExperimental data for fatigue life estimation and fatigue fractureFracture surfaces were also analyzed at various strain amplitudes. Results showed that both alloys present nearly ideal Masing behavior with symmetric hysteresis loopsHysteresis loops . The cyclic softening occurs in both alloys but the softening rate varies with alloys, which is lower in 356-T7 than 319-T7. Moreover, 356-T7 behaved more ductile while 319-T7 exhibited higher strengthStrength during cyclic deformation. 356-T7 achieved higher low-cycle fatigueLow-cycle fatigue life than 319-T7. The different LCF behavior of these two alloys may be attributed to the presence of various precipitatesPrecipitates due to the variation of Mg and Cu contents.

AlSi7Mg (A356) alloys are widely used for industrial applications due to their age hardenability and superior castability for components in near net shape. Conductivity—both electrical and thermal—is an important property for some applications in AlSi7Mg alloys. Although AlSi7Mg alloys display lower conductivity than pure aluminium, it is still important to maximize conductivity in the alloys for suitable applications. There are several metallurgical aspects to be considered in order to achieve high conductivityHigh conductivity AlSi7Mg alloys—avoiding Ti addition, removal of Ti, V, Zr and Cr as trace elements, modificationModification and spheroidization of Si eutecticSi eutectic microstructure, and formation of Mg–Si hardening precipitatesPrecipitates . These are governed by alloy composition, melt treatment prior to casting and heat treatmentHEAT TREATMENT of the cast components. In this paper, an overview and recent results of high conductivityHigh conductivity AlSi7Mg alloys are presented with regard to 1. market, 2. metallurgical factors, 3. production, and 4. optimizationOptimization and further development.

The major problem in aluminumAluminum industry is a die solderingDie soldering resulted from chemical and physical reactions of mold and molten aluminumAluminum in die castingDie casting process. The reactions lead to the formation of intermetallic compounds such as AlAl -Fe and AlAl -Fe-Si phases when the molten aluminumAluminum contains Si. The diffusion reaction causes die erosionDie erosion and forms a soldering layer on the aluminumAluminum castingCasting products leading to bad die accuracy and the quality of aluminumAluminum products. In this study, Fe and Si contents were varied simultaneously with reaction time. The thickness of the die erosionDie erosion and die solderingDie soldering layer is changed with composition of aluminum alloysAluminum alloys and reaction time. The thickness of die erosionDie erosion decreases when the aluminum alloyAluminum Alloy contains Fe. In case of the die solderingDie soldering layer, the thickness decreases as increasing Si contents in aluminum alloyAluminum Alloy . Additionally, the layer is divided into two regions and they are identified as Fe2AlAl 5 and FeAl3.

The Computational Fluid DynamicsComputational Fluid Dynamics simulation provides a useful tool to predict the temperature evolutionTemperature evolution inside the furnaceFurnace and in the material. The preheating step of the ageing treatmentAgeing treatment for aluminium alloyAluminium alloy plates from the room temperature to the set temperature was simulated by using ANSYS software. The mathematical modelThe mathematical model was validated by industrial tests. The experiments were run on an indirectly heated, fuel fired batch furnaceFurnace for aluminiumAluminium plates ageing treatmentAgeing treatment . The modelModel was run up to a temperature of 80 ℃ ± 3 ℃. The purpose of the developed modelModel is to determine the hot air circulation inside the furnaceFurnace and the cooler and warmer areas. Knowing the hot air circulation helps to position different thickness plates in the furnaceFurnace in such a way to achieve faster heating. Thus, by using the developed modelModel , the preheating stage can be optimizedOptimized by studying the influence of the batch volume, the thickness of used spacers, the dimensions of the plates and their position in the furnaceFurnace .

The suppliers of the heat treatment furnaces have created the possibility to control the distance from the top nozzles to the plate surface during the quenching by mechanical displacement of the spray nozzles. The influence of the distance between the plate and the top nozzles during the soft quenchingSoft quenching process was studied by using ANSYS finite elementFinite element soft. This distance determines the area of spray nozzles on the plates and influences the quenching process by different values of the heat transferHeat transfer coefficients. The mathematical modelThe mathematical model of the soft quenchingSoft quenching process by water spraying for a 6061 aluminium alloyAluminium alloy plate of 10 mm thickness was presented and validated on industrial equipment. Different distances between the top nozzles and the plate were simulated. The achieved results confirmed the influence of the distance between the plates and the top nozzles, during the soft quenchingSoft quenching process on the cooling rate and on the 6061 aluminium alloyAluminium alloy plate material properties.

MacrosegregationMacrosegregation formed during direct chill (DC) castingCasting of aluminumAluminum ingots will deteriorate the mechanical propertyMechanical Property of products. The characteristic of macrosegregationMacrosegregation is reported to be affected by the free-floating crystalsFree-floating crystals , which was proved to result in the center negative segregation. The motion of free-floating crystalsFree-floating crystals in ingots is numerically simulated. The modelModel is developed to incorporate fluid flow, heat transferHeat transfer , and the motion of free-floating crystalsFree-floating crystals basing on the mixture modelModel and Lagrangian approach. Efforts are made to investigate the motion of free-floating crystalsFree-floating crystals in liquid and slurry zones during solidificationSolidification of castingCasting process. In addition, distribution of the dendrites in mush and solidified zones is also studied. The variation of macrosegregationMacrosegregation with the influence of free-floating crystalsFree-floating crystals can be primarily clarified according to the results.

In the quest of averting the drawbacks of alloys of titanium in advanced manufacturing, the laser metal deposition technique is used to fabricate suitable coatings with innovative microstructural evolutionMicrostructural evolution and unique surface properties in aggressive environmentEnvironment . The vital factor to be considered during direct laser metal deposition process is the simultaneous action of meltingMelting and fusion of the coating material to the base metal. The appropriate selection of laser processingProcessing parameter produced desirable result and properties. At scanning speed of 1.2 m/min, AlAl -10Sn-5Si coating has an ultimate hardnessHardness of 463.57 HV whilst at the scanning speed of 1.0 m/min the value has decreased to 398.36 HV (65.21 HV difference). Sample AlAl -10Sn-3Si also showed the same trend in increase hardnessHardness at 1.2 m/min. While AlAl -10Sn-1Si did not follow the trend of other two coatings. The modelModel was developed to obtain insights on the behaviour of laser melted pools subjected to various process parameters. Simulation with 3D modelModel with different values of various significant processingProcessing parameters such as laser power, scanning speed and powder feed rate influences the geometry and dynamics of the melt pool, and cooling rates.

The purpose of this article is to better understand the behaviour of the residual stresses in aluminium alloyAluminium alloy plates, to control and minimize them by adjusting the quenching and the stretching process parameters. Residual stresses have usually the same role in a material as ordinary mechanical stresses, but while the stresses due to external loads can be calculated with a high degree of accuracy, the same thing cannot be said about residual stresses. The evolution of the residual stresses in the aluminiumAluminium plates and the influence of the quenching and stretching process conditions was investigated by the Hole-Drilling methodHole-Drilling method . The experiments were performed only on the industrial equipment. Plates with the same chemical composition were quenched by water sprayWater spray or by immersion in water with or without agitation of the cooling medium. Also the plates quenched by water sprayWater spray were unidirectional, bidirectional and successive stretchered. The results show the influence of the quenching conditions and of the stretching rate on residual stresses and also the correlation between the stretch rate and the residual stresses was established. Thus, the residual stresses increase from 158 MPa for quenched by water spraying to 187 MPa for horizontal quenched by immersion with agitation of the quenching water. The decrease of the residual stresses slope is reduced by the increase of the stretch rate with over 4%. The increase of the stretch rate with over 4% determines a significant reduction of the residual stresses.

The final surface properties of aluminum flat products vary depending on different processingProcessing conditions such as changes in alloy elements, different annealing temperatures, rolling parameters and surface chemicals used in the degreasing process. These changes in process parameters affects the surface roughness, surface oxide formation and structure. Thus, the next process steps such as surface pre-treatment, painting, bonding etc. are determining factors for the surface quality in processes. In this study, 1xxx and 3xxx series of aluminum alloys were examined. Different annealing temperatures between 220 and 480 °C were applied to cold rolled aluminum sheetsAluminum sheets , surface roughness and wetability (adhesion behaviour) values were examined. In addition, the effects of acidic and alkaline surface chemicals on the surface adhesion with different degreasing qualities, have been investigated depending on the degreasing parameters (immersion time, bath temperature, chemical concentration). Surface qualities were measured using different test methods such as; roughness measurement, wettability, cross cut test, cupping test, impact test and cylindrical bend test to understand physical and tribological properties of base material.

In this work the susceptibility to intergranular corrosionIntergranular corrosion of (i) different wrought aluminiumWrought aluminium alloys and (ii) various compositions of the same standard alloy was investigated with electrochemical and metallographic methods. The main difficulty in predicting the intergranular corrosionIntergranular corrosion behaviour based on the results of the electrochemical corrosionElectrochemical corrosion test is in the fact that, even when performed with the same chloride medium and under the same or similar experimentalExperimental conditions, electrochemical fatigueElectrochemical fatigue results in a different corrosion attack on the surface of aluminium-based products. On the other hand, the measure of the intergranular corrosionIntergranular corrosion is often under the operator’s influence, which is not the case in electrochemical corrosionElectrochemical corrosion testing. Therefore, the purpose of this study was to correlate the results of these two methods, enabling the accumulation of the appropriate filtered and structured data for high-quality data-driven predictions of the most stress-corrosion-resistant compositions of wrought aluminiumWrought aluminium alloys. The comparison of the IGC test and the electrochemical fatigueElectrochemical fatigue test for alloy 2024 showed similar results for an immersion time period of 9000 s. The electrochemical test revealed that corrosion progresses up to 5400 s, then it stopped. The biggest step happened from 1800 to 3600 s when the IGC cracksCracks extended up to 170 µm. On the other hand, the depth of the IGC in alloy 6082 is much shallower than in alloy 2024, especially the IGC generated with the IGC test according to PV1113. Comparing the data for the crack-penetration depth at 3600 s, the fatigue time for the 2024 alloy, and the 7200 s fatigue time for the 6082 alloy, a good correlation with the conventional PV 1113 standard method was obtained.

Transmission electron microscopy (TEM) has been employed to investigate the nature and microchemistryMicrochemistry of Grain boundary precipitatesOn the other hand precipitates in Al 7079 and Al 7075 aged at the peak and over aged conditions to correlate with the stress corrosion crackingStress Corrosion Cracking (SCC) behavior. The SCC plateau velocity in Al 7079 at T6 and T7 conditions is two to four orders of magnitude higher, respectively, as compared to Al 7075 T6 and T7. TEM studies revealed that the precipitatesPrecipitates within grains in Al 7079 at the peak and overaged conditions is mostly T-phase (Al16Zn33Mg32), while the precipitate at grain boundaries is Al-Mg-Zn type quasicrystalline precipitate (Al15Mg44Zn41). The grain boundary phase in Al 7075 at peak and over aged conditions is hexagonal η phase with stoichiometry Mg(CuxZn1−x)2. We demonstrate that Al 7079 is more susceptible to SCC as compared to Al 7075 as a result of the formation of the quasicrystalline phase with relatively high Mg content at grain boundaries.

The effect of homogenizationHomogenization on centerline segregationCenterline segregation has been studied in twin roll cast aluminum alloyCast aluminum alloy AA 8011. It is observed that second phase particles generally form when the alloyAlloy contains high Fe and Si. During twin-roll castingTwin-roll casting process, beta phase of AlFeSi segregates at the centre of the strip in the thickness range of 10–15 µm. Such phase has a needle shape morphologyMorphology that inversely affects the formabilityFormability . Phase transformation from β-AlFeSi to α-AlFeSi is found to occur when homogenizationHomogenization is carried out at high temperature. During the phase transformation, the morphologyMorphology of second phase particles also changes from needle to circular shape. Furthermore, it is also observed that the area fraction of second phase particles decreases with an increase in time and temperature. If homogenizationHomogenization temperature is increased, particle sizeParticle Size growth is found to be dominant on the spread of intermetallic particles.

Friction surfacingFriction surfacing (FS) coating layers are generated through severe plastic deformation (SPD) at elevated temperatures (≈0.8 Tmelt). Alloying elementsAlloying Elements in metals affect heat generation and dynamic recrystallization kinetics during SPD, and therefore require significant adjustments of FS processingProcessing conditions. In this study, custom made Aluminum alloysAluminum alloys (AA 6060 with additions of 2 and 3.5 wt% Mg, and 6.6, 10.4 and 14.6 wt% Si) were processed by FS. It was found that for the high-Mg Aluminum alloysAluminum alloys especially the rotational speeds require a downward adaption to achieve a steady state process. A higher content of Mg results in a reduced rate of thermal softening and more efficient heat generation. With regard to the plasticization behavior during FS, the high amount of hard phases in the high-Si alloys was expected to cause additional friction and increase heat generation. However, as the Si content increases, the process temperatures decrease. Influences of Mg and Si content on material efficiency and coating dimensions were evaluated and discussed.

In 8xxx aluminum foil alloys strengthStrength , formabilityFormability , ductilityDuctility , and softening behavior are influenced by various alloying elements. This paper provides a review about the latest findings in that field. The influence on the recrystallization of the alloying elements in their solute and precipitated form on one side and the processingProcessing route (homogenizationHomogenization , hot/cold rolling, inter/final annealing) on the other side are discussed. Particularly, the role of Fe and the emerging phases containing Fe as alloying element are discussed in detail. Finally, the results of industrially produced AA 8021 foils are presented which prove the quantitative influence of the Fe content on mechanical propertiesMechanical properties .

Dilute AlAl -Zr alloys form upon agingAging , AlAl 3Zr nano-precipitatesPrecipitates which resist coarsening up to 475 °C. Binary eutecticEutectic AlAl -Ni alloys exhibit AlAl 3Ni microfibersMicrofibers formed during solidificationSolidification which also have good thermal stability. Here, we combine both strengthening approaches and study the effects of Zr micro-additions to an eutecticEutectic AlAl -6Ni (wt%) alloyAlloy on macro-, microstructureMicrostructure and hardnessHardness evolution upon long-term aging at 350 and 375 °C. The AlAl -6Ni-0.2Zr and AlAl -6Ni-0.4Zr (wt%) alloys exhibit a dendritic microstructureMicrostructure with primary AlAl 3Zr micro-precipitatesPrecipitates . The AlAl -6Ni alloyAlloy maintains a constant room-temperature hardnessHardness after agingAging at 350 and 375 °C for 432 and 96 h, respectively, followed by a slow softening due to coarsening of the AlAl 3Ni microfibersMicrofibers . The AlAl -6Ni-0.4Zr alloyAlloy shows a strong precipitationPrecipitation -hardening response from AlAl 3Zr nano-precipitates achieving peak hardnessHardness after 48 and 24 h upon agingAging at 350 and 375 °C, respectively, and maintaining peak hardnessHardness for 768 and 264 h after agingAging at these temperatures. However, no precipitationPrecipitation hardening is occurring in AlAl -6Ni-0.2Zr, due to the lower Zr amount present in the matrix after solidificationSolidification .

We studied the possibility of improving the coarsening resistanceCoarsening resistance of nanoprecipitates with the L12 structure, in an AlAl -Zr-Er alloyAlloy system, by microalloying with slow-diffusing tungsten (W). Dilute AlAl -Zr-Er-W alloys with and without Si were prepared, cast and isochronally (3 h steps, from 200 to 600 °C) aged to understand the behavior of W and its interactions with Zr and Er in aluminumAluminum . The microstructureMicrostructure of these alloys in the as-cast and aged conditions has been studied over relevant length scales in parallel with electrical conductivityElectrical conductivity and microhardnessMicrohardness measurementsMeasurements . In addition to optical microscopyOptical Microscopy studies, local-electrode atom-probe tomographyAtom-probe tomography analyses are performed to investigate the structure of the age-hardening (L12) nanoprecipitates in selected alloys.

Laser lap welding between DP980 steelSteel and 6061 aluminum alloyAluminum Alloy was carried out using IPG YLS-6000 fiber laser, nickel foil with different thickness (0.10, 0.20 and 0.30 mm) was used as interlayer. The microstructureMicrostructure was observed by SEM, EDS was used to determine the distribution of elements and intermetallic compounds (IMC) types, and the hardnessHardness was determined by HV1000IS. The results showed that the microstructureMicrostructure in weld seam (WS) and fusion line (FL) of welded joint without nickel foil was δ ferrite and lath martensite (LM). For welded joints with nickel interlayer, the δ → γ phase transition was promoted by nickel elements. Thus, with the thickness of the nickel foil increased, the content of nickel elements in weld pool increased, resulting in decrease of δ ferrite content in WS and FL. Meanwhile, the microstructureMicrostructure in WS and FL was full LM when the thickness of the nickel foil was 0.30 mm. Meanwhile, the NixAly IMC was found in interface, which inhibited Fe–AlAl metallurgical reaction and reduced the thickness of Fe–AlAl IMC. Therefore, with nickel foil thickness increased, the content of nickel elements and the NixAly IMC increased. Moreover, the maximum thickness of the IMC layer was able to reduce to 10.66 when the thickness of the nickel foil was 0.10 mm. With the reduction of δ ferrite content in WS and FL, the microhardnessMicrohardness in WS increased with the thickness of the nickel foil increased. However, because the NixAly IMC was a soft phase, the microhardnessMicrohardness in interface decreased, significantly.

Mercury Marine has recently implemented an advanced aluminumAluminum -siliconSilicon alloyAlloy (Mercalloy™ 362) into a redesigned, lightweight gear case for use in high powered marine engines. The company is currently in the process of tuning the manufacturing process to reduce the evolution of residual stressResidual stress during the castingCasting process. Preliminary work was performed by the authors on non-machined, as-cast and T5 heat-treated gear case castings. The primary results from that study indicate relatively high residual stresses (~120 MPa) were present in the radial and hoop orientation of the as-cast gear case (Sediako in Thermec, 2018 [1]). With the expectation that the machining process would likely increase the stress throughout the gear cases, it was necessary to perform an additional study on machined gear cases in both the as-cast and T5 state. This study presents the residual stressResidual stress and strain characterizationCharacterization of machined, as-cast and T5 heat-treated marine gear cases using neutron diffractionNeutron Diffraction (ND) at the Canadian Nuclear Laboratories. A comparison of the results from this study to the preliminary results, revealed that the machining process increases the stress by approximately 45%. However, the ND results also indicate that heat treatment was successful in alleviating approximately 50% of the residual stressResidual stress in the machined and non-machine gear cases. The results from this study provide the company with valuable information for further optimizing the design and manufacturing technologies for the highly advanced lightweight marine gear case.

Constant search for materials with superior strengthStrength to weight ratio as well as high temperature resistance has triggered a keen interest on aluminum matrix composites (AMCs) for potential application in aerospace and automotive industry. For the sake of clean environmentEnvironment and low cost, industrial and agricultural wastes are been adopted in the production of AMCs. Friction stir processingFriction Stir processing technique was used to develop aluminum matrix composites with palm kernel shellPalm Kernel Shell (pks) ash particles as reinforcement. Microstructure examination was done with the aid of an optical microscope and the captured micrographs show a well imbedded and evenly distributed PKS ash powder into the aluminum substrate. Obtained micro hardnessHardness values show improvement from the beginning to the end of the process with Vickers hardnessHardness of 31.74 (Middle) and 36.11 (End). A pin on disc tribometer was used for friction testing while considering effect of load, 1 and 10 N namely. The experimentalExperimental analysis of the friction gave mean value of 0.862 and 0.828 respectively for the two loads considered. Microstructural investigation revealed a homogenous distribution of the pks ash particles into the metal substrate.

Based on requirements of automotive applications for weight reduction, aluminum alloysAluminum alloys become more popular as lightweight material. 5754 aluminum alloysAluminum alloys are commonly preferred in automotive industry due to high strengthHigh strength and good formabilityFormability . 5754 sheet materials produced by either direct chill castingCasting (DC CastingDC casting ) or twin roll casting methodCasting method (TRC) by aluminum sheetAluminum Sheet manufacturers. In present study, 5754 aluminum alloysAluminum alloys were both casted by DC CastingDC casting and TRC methods. On the purpose of good deep drawing behavior and high strengthHigh strength for automotive components, alternative thermo-mechanical processes were carried out in laboratoryLaboratory scale. Metallographic examinations were done in order to investigate influence of diversified castingCasting methods on grain structureGrain structure . Besides that, tensile testTensile Test and deep drawing test were conducted for characterizationCharacterization of specimens. SEM-EDS and SEM-EBSD analyses were fulfilled to examine the structure of intermetallic on material and textureTexture development.

In this paper, high-speed direct chill castingCasting was investigated to improve the microstructureMicrostructure and mechanical properties of AlAl -Mg-Si-Fe alloyAlloy billetBillet . With the increase of casting speedCasting speed , the size of grain decreased from 82 to 23 μm; Fe-containing intermetallic phase significantly refined and transformed from bone to short rod-like shape. The macrosegregationMacrosegregation of Mg, Si and Fe was alleviated from center to surface of the billetBillet at high casting speedCasting speed . The Mg, Si and Fe elements also had a homogeneous distribution in the grain with the increase of casting speedCasting speed . Moreover, EPMA analysisEPMA Analysis indicated that solid solubility of Mg, Si and Fe improved when casting speedCasting speed increased from 100 to 300 mm/min. HardnessHardness and tensile propertiesTensile properties all improved with the high casting speedCasting speed . The high-speed direct chill castingCasting was an effective mean to overcome the disadvantage of conventional castingCasting process.

M-HPDC is an In-Mold manufacturing process combining high pressureHigh pressure die castingDie casting (HPDC) and Injection Molding (IM) within a single die. The M-HPDC cycle starts with the injection of molten aluminumAluminum via a conventional cold-chamber HPDC process and is followed by an IM process into the same die in order to manufacture a metal-plastic hybridHybrid specimen. The new HybridHybrid -IIIChromium oxide (III) die is equipped with extensive means for temperature control, e.g. multiple cooling circuits, heating cartridges and thermocouples in order to adjust the temperature in the joining area. It is imperative to gain knowledge about the actual temperature close to the joining area and its influence on the hybridHybrid specimen. The overarching goal of the investigations is to derive design guidelines for the M-HPDC process in order to expand its applicability to complex geometries. Extensive test series are currently carried out for this purpose. The first results of these investigations will be presented.

Textures of direct chill (DC) and continuous castingCasting (CC) AA6xxx aluminumAluminum (AlAl ) alloyAlloy sheets by using X-ray diffractionX-ray diffraction method were measured. The microstructures of the two aluminum alloyAluminum Alloy sheets were studied by using optical and scanning electronic microscope (SEM). In order to make a comparison of formabilityFormability , the forming limit diagrams of the two alloyAlloy sheets were determined. The relationship between microstructureMicrostructure , textureTexture and formabilityFormability will be discussed. It was found that changes in shapes of FLDs of two AlAl alloys were caused by strong Cube with very weak S, CopperCopper and Brass textures.

PrototypingPROTOTYPING prior high pressureHigh pressure die castingDie casting (HPDC) is used for product/mold design optimizationOptimization . Plaster mold casting is a cost-efficient prototypingPROTOTYPING technique providing good surface quality and dimension accuracy, similar to HPDC components. However, the corresponding mechanical propertiesMechanical properties of a component produced with these two methods are diverging significantly, mainly due to differences in the cooling rate. This work presents a procedure to optimize the plaster mold casting for prototypingPROTOTYPING to replicate mechanical propertiesMechanical properties of a commonly used Al-Si alloy (A380). Two commercial alloys with compositions close to the A380 alloy (A356.0 and A360.2) were used. Yield strengthStrength was considered as the main design criteria, thus the target mechanical propertyMechanical Property . Tensile testing results showed that with an optimizedOptimized T6 heat treatmentHEAT TREATMENT , not only the yield strengthStrength , but also ultimate tensile strengthTensile strength Strength and elongation correspond well to the properties in the HPDC component.

The DC castingDC casting process is characterized by discontinuous cycles of castingCasting followed by a stop and set-up time. After each drop, a waiting time is required to complete metal solidificationSolidification in the ingot head and cool the ingot to an adequate temperature prior to removal using a head crane. The ingot coolingIngot Cooling time after castingCasting is an important element affecting the total cycle time and overall productivity of the castingCasting center. The objective of this work is to identify avenues to reduce the ingot coolingIngot Cooling time in the castingCasting pit to increase productivity. Two approaches were evaluated. The first one is to increase the cooling rate in the pit, and the second one is to strip the pit faster with ingots at a higher temperature. For each method, a complete characterizationCharacterization of the ingot temperature was performed. Constraints and issues were identified, and some possible solutions were explored to eliminate major bottlenecks.

Aluminium alloyAluminium alloy DC-cast ingots are widely used as flat rolled products in building, construction and automotive applications. Some of these applications require a very uniform, high quality surface appearance which is closely related to the original as-cast microstructureAs-cast microstructure . Inhomogeneity in the cast microstructureMicrostructure such as floating crystals negatively impacts the surface quality of the final product. In this study, the impact of the metal level, metal temperature, type of distributor bag and use of a skim dam were assessed. These parameters must be properly adjusted in order to obtain a homogeneous grain structureGrain structure free of floating crystals.

Piston Al-Si alloys are widely used for high-temperature applications especially in automotive industry. Copper is one of the most important elements for improving the strengthStrength at room and elevated temperatures. Other effects of Cu addition need to be taken into account as well, i.e. the changes in microstructure and the coefficient of thermal expansion (CTECoefficient of thermal expansion (CTE) ). We studied the effects of Cu addition to an AA4032 piston alloy on its structure and properties. Thermal analysisThermal analysis , metallography, thermodynamic calculations, hardnessHardness , tensile and dilatometer tests were conducted. The results showed that increased Cu addition promoted the formation of primary Si particlesPrimary Si particles in this Al-Si alloy and enlarged its solidificationSolidification range. The increase of Cu concentration from 1 to 3.5 wt% improves hardnessHardness , tensile properties, and CTECoefficient of thermal expansion (CTE) of the near-eutectic Al-Si alloys. This work contributes to deeper understanding the role of Cu in Al-Si piston alloys.

Different contents of Sc and Zr were designed on the basis of Al-3Cu-2Li alloy. The microstructure and mechanical propertiesMechanical properties of the alloys in different states of casting, homogenizationHomogenization , rolling, annealing, solution and agingAging were researched. The effect the additions of Sc and Zr in Al-3Cu-2Li alloy on the microstructure and mechanical propertiesMechanical properties was investigated. In Al-Cu-Li-Zr-Sc alloy, the refining strengthening effect is derived from the primary Al3(Sc,Zr) particles. Through hot rolling, intermediate annealing and cold rolling, it can be found that the microstructure of the final cold-rolled alloy is fine and compact with the increase of Sc and Zr content, while the tensile strengthTensile strength Strength of the final cold-rolled Al-3Cu-2Li-0.2Zr-0.2Sc alloy reaches 409 MPa and the hardnessHardness reaches 133.6 HV. After agingAging at 165 °C, the hardnessHardness of Al-3Cu-2Li-0.2Zr-0.2Sc alloys increased with the prolongation of the mean time of agingAging . The hardnessHardness of Al-3Cu-2Li-0.2Zr-0.2Sc alloy is 174.1 HV after agingAging at 165 °C/20 h, but the hardnessHardness value of Al-3Cu-2Li-0.2Zr-0.2Sc alloy does not decrease when agingAging time increases.

AlAl -Si alloys are widely preferred in the castingCasting industry due to their superior properties. When the coarse silicones are modified, the siliconSilicon structure is homogeneously dispersed and higher mechanical properties are achieved. Despite the continuous use of the modificationModification process, there are uncertain points about the working mechanismMechanism . A full understanding of the mechanismMechanism will allow for more efficient processes to be developed. In this study, the ratio of % Eut/AlAl area and SDAS was investigated by adding Sr in different amounts in the hypoeutectic Al–Si alloyAl–Si alloy . No significant change in SDAS ratio was observed. % Eut/AlAl shown differences due to modificationModification .

Recently, demand of die-cast aluminum alloysAluminum alloys for manufacturing heat dissipator with high thermal conductivityThermal conductivity increases. However, most of the commercial die-cast aluminum alloysAluminum alloys yield very low thermal conductivityThermal conductivity , far lower than that of pure aluminumAluminum for high content of alloying elementsAlloying Elements . In this paper, Three kinds of low-siliconSilicon cast aluminum alloysAluminum alloys , AlAl -(1-2)Si-1Fe-1Zn and AlAl -1Si-0.2Mg-1Fe-1Zn, are investigated for their potential to obtain the ideal combination of high thermal conductivityThermal conductivity and good castability. The work shows that AlAl -1Si-1Fe-1Zn alloyAlloy can achieve a thermal conductivityThermal conductivity of 184 W/(m K) under as-cast condition, while AlAl -1Si-0.2Mg-1Fe-1Zn alloyAlloy exhibits slightly lower thermal conductivityThermal conductivity but better castingCasting fluidityFluidity and mechanical properties, and AlAl -2Si-1Fe-1Zn alloyAlloy shows both poor thermal conductivityThermal conductivity and fludity than the others. A proper heat treatment can improve thermal conductivityThermal conductivity and mechanical propeties at the same time for AlAl -1Si-0.2Mg-1Fe-1Zn alloyAlloy .

The new type 5083 aluminum alloyAluminum Alloy can be strengthened by heat treatment with the addition of 0.6 wt% Ag. Ag increased the stability of G.P. zones which provided nucleationNucleation sites for β′′ phase. β′′ phase had an ordered cubic L12 type crystal structureCrystal structure with a lattice parameter of a = 0.408 nm and was primary strengthening phase in the new type 5083 aluminum alloyAluminum Alloy when aged at 160 °C. The tensile strengthTensile strength of the peak-aged stagesPeak-aged stages of the alloyAlloy was 448.9 MPa and the yield strengthStrength was 272.8 MPa which increased 39.9 and 88.3 MPa than the as-quenched alloyAlloy respectively. The precipitate phase at the over-aged stages was T phase which was body centered cubic structure with a composition of Mg32(Ag,AlAl )49.

Aluminum foamAluminum Foam , also known as metallic foams, has shown a combination of physical and mechanical properties which widely used in aerospace, auto manufacturing, architecture and other fields. The preparation methods for aluminum foamAluminum Foam were reviewed, the applicationApplication fields for aluminum foamAluminum Foam were introduced, and the future development trend of aluminum foamAluminum Foam was prospected.

A shift from ferrous to aluminum alloys for use in automotive engine blocks has significantly reduced the weight of vehicles and has consequently improved fuel economy while reducing harmful emissions. During the casting process of aluminum engine blocks, chilling devices are typically incorporated into the sand castings for faster cooling and to allow for a more uniform cooling rate. The effects that chills have on the alloys microstructure (i.e. size, morphology Morphology and SDAS SDAS ) and mechanical properties Mechanical properties have been studied in this paper. This study characterizes the microstructure throughout a modified 319 type aluminum inline-six engine block using scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction X-ray diffraction . In addition, mechanical testing (i.e. uniaxial tensile testing) have been performed at various depths along the cylinder web to determine the effects that varying microstructure has on the mechanical properties Mechanical properties of the alloy. The results from this study indicate that the minor variation in cooling rates led to a fine and relatively uniform microstructure; resulting in the observation of similar mechanical properties Mechanical properties throughout the entire cylinder bridge.

In order to improve the recognition rate of surface defects of aluminum sheets, we propose a new feature extraction method in this paper, called NSST-KSR. Non-subsampled Shearlet transform (NSST) method can extract flexibly multiple scales and multiple directions feature information of the image. Kernel spectral regression (KSR) method can quickly remove redundancy and interference information and select important information as features. Combining the advantages of the two methods, the extracted features are more effective and concise, and the classification is easier. The NSST-KSR was tested with samples captured from production lines of aluminum sheets, including five true defect types of point imprints, scratches, dents, roll marks and wrinkles, and three pseudo defect types of lighting variation, oil stains and water marks. The results show that NSST-KSR method can effectively improve the recognition rate of aluminum sheets surface defects.

At last year TMS, the author presented the design of cells operating at around 11 kWh/kg Al. Those designs rely on the usage of design features to limit the heat loss Heat loss of anode stubs and cathode collector bars that were not revealed in last year paper. Those design features are now revealed and explained. Furthermore, the mathematical models used to analyze design options have been modified to better calculate the impact of those design features on the cell heat balance Cell heat balance and explore with more accuracy design options to further reduce the cell power consumption while maintaining a manageable cell superheat.

A trend for the next decades is the transition of aluminium electrolysis potlines, from a stable energy supply to a highly volatile energy input, which primarily driven by the increased usage of renewable energyRenewable Energy sources on the power grid. Adapting the aluminium electrolysis process to a flexible power supply needs rethinking on a number of aspects affected by unpredictive power changes. Manipulating thermal and magnetic impacts associated with fluctuating amperage are just a few of these aspects, however main topic of this paper. Installing heat exchangers and magnetic field compensation in a potline while at the same time operating it, is a major challenge. Keeping the heat balanceHeat balance and production into a relative stable state, in a long period whilst having massive power outages, upgrading busbars design and insulating with heat exchangers in a safe routine, was the main challenge to handle. The transformation process of a potline while maintaining stability also required great cooperation between contractors and employees.

Rio Tinto has developed a busbar designBusbar Design that can be retrofitted to the Sumitomo S170 cell technologyTechnology . The new busbar designBusbar Design includes under-cell busbarBusbar and side risersSide risers . The busbarBusbar redirects current away from the existing end risers, improving MHD behaviour and cell performancePerformance substantially. The design can reduce specific power consumption by more than 5%. This paper presents the key design features and methodologyMethodology for developing a design that balances both performancePerformance and operational considerations. The results of a live test cell against predicted performancePerformance are also presented.

RUSAL is currently implementing an environmental strategyStrategy that includes increasing the number of pre-baked (PB) pot lines and implementing global environmental standards at the existing smelters. The following has been achieved: implementation of new Eco-Søderberg cells with environmental indicators that are comparable to PB cells; Construction of a testing area for inert anodeInert anode cells that are intended to replace Vertical Stud Soderberg (VSS) cells; Implementation of cutting-edge online and video systems for both emissions control and cell condition monitoring; Testing of new types of binder with either a reduced or a close-to-zero content of benzo(a)pyrene; Construction of high-performancePerformance GTCs; Development and implementation of technologies for sulfurSulfur recoveryRecovery ; SPL recyclingRecycling , solid waste treatment and recyclingRecycling . This paper provides an overview of the results of more than 10 years of efforts to reduce the environmental footprint of RUSAL’s smelters.

Copper insertCopper insert collector barCollector bar (CuCB) reduces the cathode voltage dropCathode voltage drop (CVD) along with reduction in horizontal currentsHorizontal currents in the cell. Intuitively CuCB becomes a preferred choice for cell voltage reduction, but reduced heat generation leads to shifting of liquidus isotherms towards cell centre which may affect the cell operation and will intensify the severity during power outageOutage . Therefore, 3D models were used to analyse the thermal profile, voltage, current distributionCurrent distribution , magnetic field and fluid flow for existing and CuCB cell. The CuCB was designed to have reasonable reduction in CVD and improved current distributionCurrent distribution for reducing the inter-electrode gap. The cell liningLining was modified to avoid isotherm shifts at reduced heat generation and to have lesser cooling rate during power outages. Based on the new design, one pilot cell was started at Hindalco Mahan, which is offering good performancePerformance and substantial reduction in specific energy consumptionEnergy consumption .

This paper presents technologies for liningLining the cathodeCathode with un-shaped liningLining materials that allow saving resources (required for liningLining the sub-cathodeCathode zone) and reducing the amount of waste (or spent materials). Also, the paper discusses the properties of un-shaped liningLining materials that are based on lignite semi-cokeCoke . Moreover, it describes methods and machines for liningLining the cell and re-cycling un-shaped materials. Furthermore, the paper provides information on the technical and economic indicators of test cells using un-shaped liningLining materials, including some autopsyAutopsy results for cells of different age.

Raising amperage to increase production is generally an effective way to increase smelter profitability. Three SM-17SE pots were upgraded from the aspects of busbarBusbar arrangement, cathodeCathode liningLining and alumina feedingAlumina feeding control to achieve the goals of both increasing current and saving energyEnergy . In 2017, the test pots were started up. The pots were designed to operate at 235 kA, and are now running at 240 kA. All test pots show very good stability and healthy condition. The technologyTechnology has achieved design targets and exceeded expectations. It is now considered suitable for expansion opportunities.

In the aluminum reductionAluminum reduction technology, the current in a cell is first distributed through a series of anodes before reaching the electrolytic bath and the metal pad. This can be conceptualized as a series of resistances in parallel, each with its own parameters and resulting current. In this work, a transient model of the anodic current distributionCurrent distribution is presented. This model tracks the properties of each anode (age, dimensions, presence or absence of slots) and predicts the local current, anode-cathode distanceAnode-cathode distance (ACDACD ) and current efficiencyCurrent efficiency throughout the anodic cycle. More complex phenomena, such as the deformation of the metal pad and the ledge formation around new anodes, are also taken into account by simplified laws. The model has been extensively validated based on industrial measurementsMeasurements , and can now be used to gain insight into the behavior of the pot, estimate the local ACDACD , and guide design and operating decisions.

The Hall-HéroultHall-Héroult is the major industrial process for aluminiumAluminium production. It consists of electrochemical reactionsElectrochemical reactions inside a crucible of molten electrolyteElectrolyte at approx. 960 °C. AluminiumAluminium is produced at the cathodeCathode from aluminaAlumina $$ (Al_{2} O_{3} ) $$ , while mainly $$ CO_{2} $$ is produced at the anodeAnode surfaces. Produced gas is accumulated under anodeAnode bottom surface and then periodically released to the atmosphere. Accumulation of gas increases the overall cell resistance, causing additional voltage drops and increasing power requirement. In this work, CFDComputation Fluid Dynamics (CFD) Modeling simulations of $$ CO_{2} $$ production during the Hall-HéroultHall-Héroult process are performed and the effects of gas layer and bubble dynamics are investigated. An OpenFOAM solver, based on Eulerian multiphase method has been developed taking into account the mass transfer between fluids and gas. The current passing throughout the cell is calculated with the Gauss’s law for static electric field. The modelModel used for mass transfer is the Faraday’s law of electrolysis. The numerical modelNumerical Model is validated by comparing effects of gas accumulation and release on the electrical field with experimentalExperimental measurementsMeasurements available in literature.

Startup fuses are used to protect cathodeCathode busbars from arcing damage when putting a cell in circuit. While an ideal fuse would divert all electrical current flowing through a given short-circuiting station when removing its last wedge, this is never the case in an operating cell. Fuses are part of a parallel network of conductors, therefore, the amount of current effectively diverted depends not only on their dimensions, but also on pot internal resistance at the preheating phase and on the interfaces electrical contact resistance. This article discusses the physics of startup fusesPhysics of Startup Fuses and the on-duty behavior of both bolted-on-bus and clamped specimens. Prototypes were designed using numerical analyses and then field-trialed at different amperages. Apart from validating numerical predictions, experimentalExperimental data indicated that fusing timeFusing Time may be directly estimated by pot voltage readings, if sampled raw and at high enough frequencyFrequency .

AluminiumAluminium reduction cellReduction cell exhaust flowrate is an important process controlProcess Control parameter. It must be sufficient to pull all fumes from under-hood in normal operation, during anode changeAnode Change and tapping. It should also reduce exhaust gas temperature to prevent degradation of filter bags in gas treatment centerGas treatment center (GTC) for aluminum production (GTCGas treatment center (GTC) for aluminum production ). It is believed that the duct flowrate controls cell heat balanceCell heat balance but this is disputable. It is difficult to precisely measure impact of gas exhaust flowrate on the cell heat lossHeat loss . Therefore, a modelling study was carried out to compare cell heat lossHeat loss at different duct flowrates and anodeAnode cover heights. Two different modelling approaches were used and results compared: A simplified finite element modelFinite Element Model (FEM) using empirical heat transferHeat transfer coefficients and a comprehensive computational fluid dynamicsComputational Fluid Dynamics (CFDComputation Fluid Dynamics (CFD) Modeling ) modelModel of full top part of the cell, including anodes, under-hood space and duct exhaust system. The paper discusses modelling approaches, validationValidation and results.

A new cathodeCathode design is investigated using the finite elementFinite element method, in an attempt to improve the energy efficiencyEnergy efficiency of a cell and reduce the premature wear of the cathodeCathode due to a non-uniform current distributionCurrent distribution . This new design relies on cylindrical collector bars including copperCopper inserts and eliminates the need of a cast iron interface in order to improve contact between the carbon blocks and the collector bars. The thermo-electro-mechanical modelModel developed includes contact interfaces to simulate the contact between the different materials and is employed to determine the optimal configuration. Various geometry and design parameters are explored and their effect on both voltage drop and current distributionCurrent distribution are highlighted. Simulation results indicate that a substantial voltage drop reduction and more uniform current distributionCurrent distribution could be achieved.

To achieve the applicationApplication of aluminum electrolysis cellsAluminum electrolysis cells to accommodate unstable wind power, a transiently coupled thermo-electric modelModel of a 420 kA grade aluminum reductionAluminum reduction cellReduction cell is established to calculate and analyze the changes of side ledgeSide ledge and side shell heat lossHeat loss under current fluctuations. The calculation results show that when the current is increased by 2%, the side ledgeSide ledge and the heat lossHeat loss rate does not vary markedly; when the current increases by 5, 8 and 10%, the side ledgeSide ledge melts at certain point within 8 h, and the heat lossHeat loss rate of side shell near the melt domain changes most rapidly. The ledge thickness under normal current and current fluctuations are calculated. Comparing the results respectively with the test data obtained from industry cells and results calculated by this modelModel and the traditional loop iteration, this modelModel has accuracy and reliability. Based on it, process adjustment measures are proposed and verified by simulation calculations.

Alumina, alongside with electricity and carbon, is the raw material used for production of aluminium in the Hall-Héroult process. An efficient dissolutionDissolution process is important to acquire stable conditions for the cell, resulting in lower energy consumptionEnergy consumption . Under certain conditions, the alumina will not dissolve upon addition but remains afloat on the bath surface as a so called raftRaft . The conditions under which the rafts form are still not fully understood, although it is likely that their behaviour is influenced by operational conditions which in turn depend upon bath and alumina properties. In order to obtain more knowledge on the conditions for raftRaft formation, an industrial measurement campaign was performed at Alcoa Mosjøen in which raftRaft behaviour was recorded alongside collection of bath and alumina samples as well as the rafts themselves. The current paper describes the procedure utilized for data collection together with an analysis of bath and alumina properties, aiming to correlate these with raftRaft flotation times. RaftRaft floating times were found to vary between 5 and 140 s during normal operating conditions.

With the general tendency of increasing current and decreasing ACDACD in the aluminium electrolysis cells, the challenge of assuring of good control of alumina feedingAlumina feeding is more and more important. Unfortunately, a significant part of the cold injected alumina forms floating rafts instead of dissolving fast. The temporary solidified bath around the rafts delays the alumina dissolutionDissolution and promotes agglomeration, increasing the possibility of sludgeSludge formation. As both the solidifying bath around and in between the particles and the sinteringSintering of alumina increase mechanical strengthStrength , the kinetics of those phenomena can be followed by measuring the mechanical resistanceMechanical resistance of rafts removed from an electrolytic cell after different time periods. The goal of this paper was to examine the correlation between raftRaft exposition time to the hot bath and the resulting mechanical resistanceMechanical resistance . For this reason, alumina rafts were produced under well controlled conditions in laboratoryLaboratory in order to carry out mechanical flexion tests on them. Results showed a gradually increasing mechanical resistanceMechanical resistance with exposition time.

Alumina feedingAlumina feeding at regular intervals requires optimizationOptimization for the feeder positions, their number, the feed amount and the timing. The specific composition of the feed material could be variable in the particulate material sizes and the specific density. The addition of particles of various sizes is treated by Lagrangian methods following the tracks of inertial particles subject to drag in the turbulent electrolyte flow. The emphasis is on the large scale circulation which is essential to achieve the desired uniform alumina composition over the whole cell. Each particle is permitted to gradually dissolve in dependence of its individual size and the local concentration field value below the saturation level. This time variable source is used to follow the concentration field development on the Eulerian grid. The newly developed modelling technique is implemented as an add-into the specialised MHDMHD software for commercial cell modelling and optimisation.

To improve the operation of the aluminum reductionAluminum reduction technology, each step of the alumina incorporation into the bath needs to be understood. The mathematical model presented in this paper, uses the Discrete Element MethodDiscrete element method (DEM), based on the description of the interactions between the particles and surrounding liquid, solving the kinematic equations. First, the description of particle-particle interactions was validated by experimentalExperimental values of bulk density and angle of repose. Next, the interaction of particles with the liquid when arriving onto the free surface was added. Furthermore, modelling of phenomena like aggregate formation, breakup and dissolutionDissolution requires the quantitative description and integration of further physicochemical knowledge. The number of injected powder particles during feeding is in the order of few hundred million. Following of such a number of particles is very much demanding computationally. Consequently, it is primordial to determine the minimal number of particles that reproduces correctly the physical reality.

As alumina particles are fed to aluminium reduction cells, a frozen layerFrozen layer of bath is typically formed on the particle surface, due to the relatively low bath superheat. For particles in close proximity, platelets with frozen bath can be formed, resulting in agglomerates (rafts) containing solidified bath and alumina. The formation, flotation and break up of these agglomerates is determined by macroscopic properties (i.e. size, density etc.) which in turn is related to microscopic properties, i.e. how grains are interconnected. The formation of rafts delays the dissolutionDissolution of alumina and thus adversely influences the conditions in the pot. In order to obtain more knowledge on the conditions for raftRaft formation, an industrial measurement campaign was performed at Alcoa Mosjøen in which raftRaft where collected under different operating conditions. Rafts have been characterized by micro computed X-ray tomographyX-ray tomography Tomography (μCT) to reveal the macroscopic properties i.e. porosityPorosity , while energy-dispersive X-ray spectroscopy (EDS) coupled to SEMScanning Electron Microscope (SEM) and XRD has been adopted to identify the chemical composition throughout the raftRaft . Results indicate considerable variations in macrostructure between different samples and also large differences within the same sample, depending upon the vertical position.

ScalingScaling in distribution pipes for secondary aluminaAlumina is a major issue in aluminiumAluminium smelters. The scale is formed inside the distribution pipes, and gradually reduces the cross section that is available for aluminaAlumina transport. The scale cannot be removed without dismantling the transport pipes and using chemical and/or mechanical treatments. This leads to interruptions in normal operation, requires additional labour, and a stock of additional pipe sections. To get a better understanding of the scale formation mechanisms, the rate of scale growth was monitored by acoustic measurementsMeasurements in a transport pipe section at an aluminiumAluminium producing plant over a period of several months. Correlation between growth rate, and recorded parameters from the associated pots, fume treatment system and meteorological data were studied. In addition, samples from the actual scale were examined by SEM, TEMTEM and AFM to investigate the microstructureMicrostructure and chemical composition.

A cylindrical foulingFouling probe or “cold-fingerCold-finger ” has been used to investigate foulingFouling from aluminiumAluminium production off-gas. The probe was located upstream from the off-gas cleaning system. Surface deposits have been collected for further analysis by EPMA and XRDXRD , and compared with off-gas dust and old scale samples collected in the same experimentalExperimental site. Cross-section micrographs of the deposit surfaces have been obtained to highlight the differences in surface structures formed on the upstream and downstream faces of the cold-fingerCold-finger . Strongly adhered hard scale formed after only two days in the upstream face of the probe. Loosely attached deposits accumulated downstream, which consisted of distinguishable particles of AlAl 2O3, spherical Cryolitic bathBath condensates and Ni-S phases. The hard scale was rich in small bathBath condensates (NaAlF4) that form a tight network keeping together the larger particles. The deposition of those particles is suggested to be a key in scale formation.

Dry granular refractory powders commonly called dry barrierDry barrier mixes (DBM) have been examined under field conditions. Cell autopsies were conducted on ten cells at five separate locations. The cells contained two different types of DBM. The autopsies showed that one of the DBM types performed well, with formation of the usual barrier and preservation of the underlying insulation materials. The second DBM type did not form the barrier, and the insulation materials were attacked and degraded by the cathodic bath. The insulation degradation was also indicated by a rise in shell bottom temperature after about two years operation.

Cell liningLining design must ensure the presence of solidus isotherm in the upper refractory layer to maintain the pot thermal balance. The depth of melt penetration in liningLining depends on the endurance of refractory layer. The melt penetration causes the mineralogical transformation of refractory layer, which acts as a barrier for further penetration. However, the barrier resistance is dependent on the chemistry of transformed phases of refractory material. This study outlines an on-field investigation of cell lining materialsCell lining materials . A detailed autopsyAutopsy of a high amperageHigh amperage cell has been performed to identify the probable causes of reduced cell life. The autopsyAutopsy results exhibit substantial deterioration of powdered dry-barrier refractory layer at an early age of cell life, leading to premature cell failure. The greater percolation of vitreous phases through the dry-barrier could be attributed to its pulverulent nature resulting in higher permeability than the refractory bricks of similar composition.

The bottom thermal insulating layer in aluminum electrolysis cellsAluminum electrolysis cells is normally well protected from chemical attacks by a refractory layer. However, autopsies of spent cathodeCathode liningLining have shown that sodium vaporSodium Vapor may reach and react with the thermal insulating layer, thus affecting the thermal balance and structural integrity of the entire electrolysis cellElectrolysis cell . Here, we report on a new laboratoryLaboratory test, named Na-tg test, where commercial thermal insulating materialsThermal Insulating Materials are exposed to sodium vaporSodium Vapor at controlled temperature and sodium partial pressure. The weight change of three commercial insulation materials was measured as a function of time at various temperatures and partial pressures of sodium. The exposed materials were investigated with respect to changes in the microstructureMicrostructure , chemical and mineralogical composition, due to the reaction with sodium. The findings are discussed with respect to the chemical durability of the three thermal insulating materialsThermal Insulating Materials .

The aluminum reductionAluminum reduction reactions in the Hall-HéroultHall-Héroult process are responsible for approximately 85% of the net carbon consumptionCarbon consumption in the electrolysis cellElectrolysis cell by reaction of oxygen with the anodeAnode , producing carbon dioxide. Some of this reacts back with aluminumAluminum to produce carbon monoxide and this part is responsible for current efficiencyCurrent efficiency loss. Some other anodeAnode reaction mechanisms: anodeAnode air oxidationOxidation , Boudouard reaction and carbon dust generation are responsible for excess carbon consumptionCarbon consumption . Studies have shown that to improve cell economics and reduce net carbon consumptionCarbon consumption in the cell, focus needs to be put on the quality of raw materials, improvement of the anodeAnode manufacturing process and finally protecting the anodeAnode from air oxidationOxidation . Air oxidationOxidation of the anodeAnode takes place on the upper part of the anodeAnode surface. In this paper, EGA is presenting an innovative approach to protect anodes in the cell by using thermal arc spray technologyTechnology to coat prebaked anodes with aluminumAluminum . The EGA technologyTechnology has shown improved penetration of aluminumAluminum in the porous surface area of the anodeAnode , which reinforces the adhesion of the aluminumAluminum coating layer, while preventing any impact on cell metal purity because the coating is pure aluminumAluminum .

This paper comes up with a new baking approach, high temperature gas baking technologyTechnology , based upon aluminiumAluminium cells characteristics and raw materialRaw material properties. Research achievements have been widely used in actual practice after numerous laboratoryLaboratory and industry tests. It turns out that high temperature gas as heating media is able to ensure uniform surface temperature distributionTemperature distribution of cathodeCathode liningLining . What’s more, it reduces the possibility of paste and carbon blocks oxidationOxidation damage during the baking process. Its good baking results create favorable condition to prolong a cells service life. This approach is also proved to be energyEnergy -saving, safe and environmentally friendly.

This paper focuses on steelSteel -aluminum Aluminum welding technologyTechnology and full-section vertical weldingVertical welding technologyTechnology for large section worksLarge section works mainly used in aluminum reductionAluminum reduction industry. Direct welding between steelSteel and aluminumAluminum would form brittle chemical compounds and cracksCracks in the joints. Research in this paper showed that proper transition layerTransition layer metal as brazing filler metal, with heat inputHeat input management during the welding process could effectively restrain the compoundCompound formation and reduce cracksCracks tendency as well. Factors that influence the compoundCompound formation have been found from numerous tests, through which we can get good welding joints with shear strengthStrength above 110 MPa. In view of current shortcomings of traditional repair methods about large section worksLarge section works during aluminum reductionAluminum reduction process, this paper comes up with a vertical weldingVertical welding technologyTechnology by which the joints can have the equal property of the base metals. It adapts to large section welding between steelSteel and steelSteel and between aluminumAluminum and aluminumAluminum Actual practice proves that it already has fulfilled the requirements of wide applicationApplication

Bath of the aluminum reductionAluminum reduction cell (as a cell itself) is a dissipative system. Important parameters of its welfare among others are: proper volume, shape, potential distribution in the anode-cathode space (ACS), direction and value of the electrolyte velocity. Using indicatorIndicator (SrCl2) introduction, volume of the electrolyte V is determined. Derivation ∂V/∂I = 10 dm3/kA is found. Bath velocityBath velocity (2–15 cm/s) and its direction using thermographic and hydrodynamic methods are ascertained. Velocities distribution is given.

As a protective top layer of an aluminium reduction cell, crust is a consolidation of anode cover materialsAnode cover materials which are made of a mix of crushed bath and alumina. Crust through its strengthStrength and barrier properties (air, HF) plays a vital role in maintaining overall heat balanceHeat balance , protecting anode and controlling fluoride loss. Numerous studies have investigated the crust formation. However, there is currently a significant knowledge gap regarding the microstructure and mechanical propertiesMechanical properties of crust. The mechanical propertiesMechanical properties of crust are important for the recycling of the material as crushed bath which will then become new cell crust. This research has conducted the microstructure and compressive deformationCompressive deformation analysis on a range of crust samples for the first time. The crust samples from industrial cells have been divided into two categories: drop and shattered (DS) and uncrushable (U) crust samples. Both DS and U crust samples have shown brittle fracture, but the compressive deformationCompressive deformation of U samples shows unique plateau deformation and hardening stages, which is due to well-developed corundum and its well-spread interlocking network with bath structure.

It is known that the sideledgeSideledge in aluminium cells is thinner than elsewhere at the level of the metal-bath interface. The present paper discusses three possible mechanisms for this local thinning or “trenchTrench ” formation. These are: (i) High local heat transferHeat transfer coefficient related to waves at the metal-bath interface, (ii) High local overall heat transferHeat transfer coefficient between metal and ledge related to the geometry of the lower part of the metal-bath meniscus, and (iii) Mixing of bulk bath and a bath filmBath film containing alumina particles at the metal-bath meniscus region, leading to high local superheat. Analyses of the lower part of the ledge revealed that the ledge contained substantial amounts of alumina, and it was shown by calculation that alumina particles can be lifted by the bath filmBath film between the metal and the ledge. The three explanations for trenchTrench formation do not exclude each other.

Hall-HéroultHall-Héroult electrolysis cellElectrolysis cell based on prebaked anodePrebaked anode technologyTechnology is continuously disturbed by anode changeAnode Change operations. Insertion of a cold anodeCold anode in a cell will freeze a layer of molten cryoliteCryolite under it and thus greatly affects, among others, the thermal balance and electrical distribution. To better understand the evolution of the frozen layerFrozen layer and its impact on the cell performancePerformance an experimentalExperimental campaign has been performed on sixteen anodes having between 15 min and 6 h of operation. The selected anodes were instrumented to keep track of the temperature and voltage drop evolutions while the frozen layerFrozen layer thicknesses were estimated by image analysisImage Analysis after the anodes were removed from the cell after the designated time. Results show that the frozen layerFrozen layer completely disappeared after three hours of operation and before the anodeAnode reaches a thermoelectrically steady state.

In this paper we describe recent laboratoryLaboratory aluminum electrolysisAluminum electrolysis tests with multiple vertical non-consumable electrodesElectrodes in a low temperature electrolyteLow temperature electrolyte . The anodes were cast Cu/Ni/Fe alloys and the cathodes hot pressed low grain size titanium diboride (TiB2). Electrolysis tests were carried out in a low temperature electrolyteLow temperature electrolyte at a current density ranging from 0.5 to 1 A/cm2. The experiments were run with three vertical electrodesElectrodes , with two cathodes and one anodeAnode , with the anodeAnode placed in the middle. The oxide coating formed on the anodeAnode was studied with scanning electron microscopy (SEM) and impurities of the aluminumAluminum obtained were analyzed. The results of chemical analysisChemical Analysis show that impurities from the anodeAnode were less than 0.2 wt% in the aluminumAluminum obtained, the major impurity being iron, about 0.1 wt%.

40 years ago W. Haupin stressed that anodeAnode overvoltages on the carbon materials have a scatter more than 300 mV under the same current density. This is a reason to attempt to find out the reason for greater differences because decreasing the overvoltage promises high energyEnergy saving. Experiments in lab.cells in galvanostatic conditions have been conducted to determine the overvoltages for the smelter anodes used in Sayanogorsk and Boguchany smelters (Russia) (more than 80 curves currents-overvoltages are received). Overvoltages are compared with other carbon block properties. Recommendations to use these values as a parameter of carbon block quality were made.

Fluid flow hydrodynamics in the aluminum electrolysis cellElectrolysis cell has been studied through numerical simulations for decades. However, there is little to no available experimentalExperimental data to validate velocity profiles obtained from these numerical simulations. Velocity measurementsMeasurements inside the electrolysis cellElectrolysis cell is difficult in practice, due to being chemically aggressive, opaque and at high temperature. A new attempt is undertaken to measure molten aluminum velocity with a drag probeDrag probe inspired from a proven device first used in wind velocity measurement. The new device is designed to minimize vortex shedding, to increase the drag coefficient and to be applicable in a harsh environmentEnvironment . This paper presents the probe adapted for the electrolysis cellElectrolysis cell , its calibration and validation method in a water channel at room temperature, and some results obtained in electrolysis cellElectrolysis cell .

In addition to the conventional electrochemical reaction in Hall-HéroultHall-Héroult electrolysis process where the aluminaAlumina is reduced to liquid aluminumAluminum , the co-evolution of anthropogenic perfluorocarbonPerfluorocarbon (PFC) gases, namely tetrafluoromethane CF4 and hexafluoroethane C2F6, was occasionally detected during the electrolysis process. In Emirates Global AluminiumAluminium (EGA), along with the continuous amperage creepAmperage creep program, incremental increase in anodeAnode dimensions and associated reduction in cell anode-cathode distanceAnode-cathode distance (ACDACD ) to satisfy cell energyEnergy requirements, the company has focused its efforts on improving the advanced cell control algorithm which has assisted EGA technologies to operate at a high current density while maintaining low PFC emissions. As part of a continuous performancePerformance enhancement program, EGA has initiated a program to understand the temporal and spatial changes in cell conditions that cause the co-evolution of PFC emissionsCo-evolution of PFC emissions . The work included studies to gain insights in major events where the co-evolution of PFC emissionsCo-evolution of PFC emissions was detected using state of art continuous individual anode current monitoringContinuous individual anode current monitoring , along with continuous monitoring of PFC emissionsContinuous monitoring of PFC emissions in reduction cells.

In 2012, Alcoa started an initiative to sustain the operation at the Baie-Comeau aluminumAluminum smelter in provision of creeping the amperage of potlines by more than 7%. As part of this initiative, solutions needed to be identified to stabilize the operation of the four Gas Treatment Centers (GTCs) and ensure compliance with a new emission limit for total fluorides (TF) of 0.65 kg TF/ton AlAl . The project is an engineering alliance project jointly executed by a team of Alcoa and Hatch specialists. The first stage was to identify which tools were available to the smelter to reduce their emissions. The impact and costs were evaluated after which a strategyStrategy was formulated. Following Alcoa procedures for approvals, three improvement projects were funded. These were (1) the installation of extended surface filter bagsExtended surface filter bags in the GTCs, (2) new fresh aluminaAlumina GTCGas treatment center (GTC) for aluminum production distribution systems, and (3) a refurbishment program for the GTCGas treatment center (GTC) for aluminum production collector ducts. This paper highlights the process for developing the strategyStrategy to lower emissions and how the three individual projects were executed with one common goal. The paper concludes with the outcomes and the overall results achieved in the fluoride emission reduction.

Climate change challenge leads government to commit themselves to a greenhouse gas reduction target and to adopt Greenhouse gas (GHG) regulation including sampling and monitoring. By regulation, all the aluminumAluminum smelters in Québec using the slope method must validate its PFC slope at least every 36 months. This is required even more often if a change occurs in the control algorithm that affects the intensity or duration of the anodeAnode effects or when a change occurs in the distribution or duration of anodeAnode effects. The three aluminumAluminum smelters operated by Alcoa located in Québec have implemented an anode effectAnode effect assessment, which includes, among others, pot start anode effectAnode effect data and reviews of the distribution of anode effect durationDistribution of Anode Effect Duration . With the analysis of the monitoring data obtained from the anode effectAnode effect sampling of pot starts, as well as with high and low voltage anode effectAnode effect measurementsMeasurements it is the objective to seek more accurate PFC slope determination for better reporting purposes.

Electric Arc FurnaceElectric Arc Furnace (EAF) steelmaking requires the addition of carbon for a variety of reasons including reducing oxides (including iron) in the slag, acting as a combustible fuel source and adjusting the carbon content of the final steelSteel product, and consequently liquidus of the steelSteel and quality of the finished product. Ideal carbon sources for the EAF require high carbon content and low sulfurSulfur content. Spent pot liningSpent Pot Lining (SPL) from the electrolysis of aluminumAluminum meets this requirement with the carbon content varying on its initial position in the Hall-HéroultHall-Héroult electrolytic cell. SPL also contains significant amounts of silica and aluminaAlumina , which are also common in steelmaking slags. SPL as a whole could both provide the necessary carbon for the process, as well as potentially replenishing the slag with fluxFlux . The present study will investigate the potential of using SPL as an EAF fluxFlux and the effect of varying parameters of SPL addition will be reported.

Recently, the application of SPL in metallurgical industry has gained significant attention since SPL was proved to have an indelible potential to be applied in pyrometallurgy as a low-cost fuel. However, the volatile fluorides in SPL, especially, NaF and Na3AlF6, limit this application due to environmental concerns, and practical/engineering issues. In this manuscript, the new vacuum distillation method (VDM) was recommended to pretreat SPL first cut below 1000 °C to separate volatile fluorides and graphite. The products, leachable fluorides and carbon enriched residue, are expected to be reused in metallurgical industries for cost-saving. To confirm the feasibility of this idea, pure fluorides, artificial fluorides-graphite mixtures (NaF, Na3AlF6, CaF2, C) as well as SPLSpent potlining (SPL) were submitted to the VDM process. The migration behavior of the components during VDM treatment has been studied, and soluble fluoride content in the VDM treated residues was examined to draw a VDM map for fluorides treatment. The overall goal is to develop an environmentally friendly technique to extract the economic value of SPLSpent potlining (SPL) in an efficient manner.

During dry scrubbing, aluminaAlumina and pot gas are distributed inside the GTCGas treatment center (GTC) for aluminum production into multiple (typical 10–30) filtering modules where the adsorption of HF takes place on the surface of the aluminaAlumina . Unintended distribution patterns due to blockages or mechanical failures inside the reactors and filter modules may give too high HF emissions due to oversaturation of the aluminaAlumina inside the various modules. Although not widely implemented yet, several systems are available today for HF monitoringHF monitoring in individual modules. These systems will be reviewed in this paper. The capabilities of the HF extractive multipoint method are verified with manual measurementsMeasurements on an 18-compartment size GTCGas treatment center (GTC) for aluminum production in the Middle East. HF molecules have a higher affinity to the aluminaAlumina surface when compared to SO2 molecules that are also contained in the pot gas. When HF molecules diffuse to the aluminaAlumina surface, SO2 molecules are pushed off because of the weaker bond to the aluminaAlumina surface. Because of this phenomenon the system is therefore capable of giving off an early warning about 2–3 h ahead before HF emissions start to exceed normal limits when SO2 concentration monitoring is added to the individual filter modules. This principle is also described in this paper.

Carbonyl sulfide (COS) is sulfurSulfur pollution gas which could cause serious adverse effects on human health and environmentEnvironment . OxidationOxidation of COS to SO2 is a potential method for COS removal. Study on COS oxidationOxidation reaction mechanismMechanism has a great significance in COS desulfurizationDesulfurization . In this paper, a Density Functional Theory (DFTDFT ) approach was adopted to investigate the COS oxidationOxidation reaction mechanismMechanism . The results show that three groups products can be generated in COS oxidationOxidation , CO2 and SO, SO2 and CO, O3 and CS, respectively. CO2 and SO are found to be the dominating products. Different intermediates can be formed when COS encounter O2. Among which, a triplet intermediate is proposed to be formed primarily, and then the triplet intermediate breaks up into two molecules, CO2 and SO.

Prolonged power outages are the major cause of inadvertent pot line shut downs in the primary aluminum industry (Kjar and Keniry in Reducing the impact of power supply interruption on potroom operations, 2007; Tabereaux in Light metals, pp. 1039–1044, 2010; Øye and Sørlie in Aluminium International Today, 2011; Dupuis and Tabereaux in Modeling cathode cooling after power shutdown, vol 1–2, 2012 [1–4]). The rate of incidence of such events has been high over this past decade and in recent years it appears to be accelerating. The design of high amperageHigh amperage cells to be able to rapidly shed heat during operations is an emerging factor of risk when compared to older cell designs. Each event of an inadvertent shut down can cost tens of millions of dollars, most of this is from lost production. In this paper the authors explore the variety of root causes that have been behind extended power interruptions that have led to an inadvertent shut down of a pot line(s) and the recoveryRecovery factors that may be involved with such an event. This will include an exploration of the typical time line that is involved from shut down through the restartRestart of lost capacity.

Always striving to increase molten aluminumAluminum annual production, since its commissioning, Alcoa Aluminerie de Deschambault has used its boosterBooster section to test new pot designs and technologies at higher amperage. Learnings from this section are later transferred to the whole potline, which has enabled continuous amperage increase from the original 300 kA nominal capacity. However, the smelter recently set a new goal for high amperageHigh amperage operation, requiring major modificationModification and extensive testing in its boosterBooster section. Higher boosterBooster capacity was required; a magnetic compensationMagnetic Compensation loop was also installed, and several anodeAnode plant improvements were made. After careful planning and execution of the capitalCapital project, operation of different pot designs was demonstrated at high amperageHigh amperage for a five month period. This paper presents results from some of the special measurementsSpecial measurements taken during this first step of high amperageHigh amperage operation, as well as key pot performancePerformance indicators.

Recently, “Maximum Achievable Control TechnologyTechnology ” (MACT) floor regulationsRegulations have been implemented in the US for total fugitive particulates from aluminium smelterAluminium smelter potlines; similar regulationsRegulations also now apply in Canada and the EU. These highlight the challenge that smelters face in meeting increasingly stringent air quality limits. For any pollutant, the first step in establishing an effective mitigation strategyStrategy is understanding the key sources of emissions. Here we report the results of a time-resolved study that examined the response of fugitive dust emissions to operations in the potroom over an entire work cycle. Identical sets of real-time dust monitors were located at both the potroom roof and floor level between cells. This built upon an earlier study on the composition of potroom dustPotroom Dust , involving several prebake point-fed technologyTechnology smelters. Similar to fugitive HF, it was found that the changing of prebaked anodes was a major contributor to fugitive dust in the potroom. At this potline, other contributors to fugitive roof dust include metal tapping, loading of cover material and mechanical sweeper vehicle movements. As expected, operations related to solids handling/transport were found to release only fugitive dust, with minimal HF emission.

With increasing cell amperage and size, the cell control technologyTechnology has also evolved to ensure good aluminaAlumina dissolutionDissolution and distribution. Renukoot smelter has about 60-year-old technologyTechnology , being sustained through continuous upgradation in the design and the control system. Renukoot pots operate at a very high ratio of aluminaAlumina feed to electrolyteElectrolyte volume as compared to modern smelters. This paper elaborates on the improvement in existing control software with prevailing hardware limitations. A new alumina feedingAlumina feeding strategyStrategy was developed by incorporating the distributed feed approach consisting of underfeed and overfeed cycles. This resulted in reduced variation of alumina concentrationAlumina concentration from 1.68 to 0.89%, thereby increasing the cell stability with reduced electrolyteElectrolyte temperature variation and reduced tendency of sludgeSludge formation. It also maintains the alumina concentrationAlumina concentration on the leaner side, while maintaining the anode effect frequencyAnode Effect Frequency . The new logic incorporates advanced statistics for making more accurate and quick decisions, with reduced human intervention.

RecoveryRecovery of lithium from lithium-rich electrolyteLithium-rich electrolyte has attracted worldwide attention because of issues from both electrolytic aluminium production and environmental impacts. Lithium carbonateLithium carbonate preparation from lithium-rich electrolyteLithium-rich electrolyte by H2SO4 leaching, removing impurities and lithium precipitationPrecipitation with Na2CO3 was investigated in this work. About 98% Li was leached using 6% H2SO4 at 80 °C for 1 h at a solid to liquid ratio of 1:2. In addition, the Li2SO4 in the leached solution was directly purified to a final pH of 11 with NaOH and 3 g/L EDTA additions. After further precipitationPrecipitation with 290 g/L Na2CO3 at 95 °C for 50 min, 99.5% Li2CO3 was obtained. With this research, it is expected to potentially design processes for lithium-rich electrolyteLithium-rich electrolyte recycling with high industrial viability.

As production capacity increases, many aluminumAluminum smelters are facing a growing challenge in energyEnergy saving and consumption reduction. Traditional studies on those above mentioned issues are more concentrated on improvement of process, design and equipment level. At present, there are few systems using remote technical diagnosis for pot operation in the world. In comparison, the technologyTechnology of “remote data-diagnosis technologyTechnology service” (RDTSRDTS ) developed by GAMI is a diagnosis platform based on pot production and operational data and built on GAMI’s control system and process instruction system. This new technologyTechnology develops a systematic solution and standard process controlProcess Control method for designing, controlling and diagnosing on energyEnergy saving and consumption reduction. Up to now, it has provided technical diagnosis for more than 4 smelters. As a result, a good effect of 0.5–1% improvement of direct current efficiencyCurrent efficiency and 100–200 kWh/t-AlAl energyEnergy saving has been acquired for whole pot line after RDTSRDTS applied for 3 month. (It refers to remote technical service effect only, not including other improvement by this technologyTechnology .)

The inherent risk associated with direct chill castingCasting is well known in the AluminiumAluminium business. During the last decades numerous innovations have been made to limit and control this risk and avoid injuries and damages to equipment. Anti-explosion coatings are now industry standard, and many design and process standards are widely accepted and used. AutomationAutomation of many of the manual tasks is now common in the industry. However, some manual tasks in hazard zones are still common. This includes preparation of casts, taking samples for chemical analysisChemical Analysis and inspect starter blocks prior to castingCasting and ingots during castingCasting . Hycast and Hydro are now starting to utilize new digitalDigital technologyTechnology to eliminate unwanted manual tasks. This paper describes some of the new technologies Hycast and Hydro are developing to achieve our goal “no personnelPersonnel in hazard zones” and some results and experiences from these technologies.

The chemical composition and cleanliness of molten metal is of fundamental importance in metal production. Traditional methods to test the chemical composition of a molten bathBath requires periodic sampling and the use of a lab based spark optical emission spectrometer (OES). Laser-induced breakdown spectroscopy (LIBSLaser induced breakdown spectroscopy (LIBS) ), has been shown to be a useful tool for quick, reliable analysis of molten metal in a production setting in situ and in near real time. LIBSLaser induced breakdown spectroscopy (LIBS) uses a high energyEnergy laser to fire into the melt and creates a microscopic plasma that in turn emits light that is characteristic of each element type and its concentration present. A spectrometer is used to identity each element and its concentration within the melt. A LIBSLaser induced breakdown spectroscopy (LIBS) system, marketed as OnSpecOnSpec® has been developed for the aluminumAluminum industry to provide real-time bulk metal chemistry of molten metal in both furnaceFurnace and launder applications. The same OnSpecOnSpec® hardware can also be configured to measure melt cleanliness, providing information about the loading, size distribution, and chemistry of inclusions. The ability to measure and characterize inclusions is currently in the research phase. A patent has been issued, another is in process, and another is being written. This paper reports on successful field tests conducted of the OnSpec® systemOnSpec® System at various aluminumAluminum facilities and discusses its potential applications and benefits.

It is a reality that operating ‘world best practice’ technology will not necessarily guarantee achieving ‘nameplate’ capabilities. Fully automated ‘hands-free’ sheet ingot casting is the goal of Trimet Essen, as it is for others in the industry. TRIMET has nonetheless demonstrated sustained improvements with its existing DC casting technology. Operation of existing plant to highest capability is necessary not only for best process results, but also to attract investment capital. This paper describes a number of steps taken to improve casting safety, pit recoveries, ingot quality and throughput, this last indicator by reducing the number of false start-ups. Additionally, the adopted measures represent necessary foundations for the transition to ‘hands-free’ casting.

High quality aluminum billet casting requires a very good control of the process parameters. After removing the billets from the casting pit, two quality control inspections are usually performed. A first one is usually performed by an inspector for the surface and shape quality of the billet and a second one for its internal structure using ultrasonic technology. STAS has recently implemented, in a cast house in Canada, a new equipment named the “BSI3D” for Billet Surface Inspection in 3D. This equipment is fully automated and uses state-of-the-art proven 3D scanning and image analysis technologies. The BSI3D is a fully objective and consistent machine that can detect and record the surface defects characteristics. It is also programmed to precisely evaluate the bending of the billets i.e. straightness. This new equipment allows for optimization of the casting process, helps to improve the billet recovery rate and reduces overall operating costs. This paper presents an overview of this equipment, its performances and benefits.

A promising approach to the rapid inspection of inclusions in wrought aluminium alloys is optical emission spectroscopy (OES). However, in order to separate the peaks corresponding to particular inclusions from the peaks obtained from various microstructural features in the matrix, an advanced filtering of the OES spectrum is necessary. The methodology developed in this work is based on big-data-driven predictions of whether an on-line analysed sample is good or bad. A sufficient amount of relevant data, necessary for data-driven predictions, was established by the systematic quality control of samples of AA6082 using optical and scanning electron microscopy and by analysing the same surface using OES. By following a machine-learning process, an algorithm was developed to enable the on-line division of the samples into good and bad, based on criteria received from the casting house. Although the obtained results are promising, further improvements are necessary before this method can be validated for use in regular production.

The automotive sector is particularly important for the aluminium industry, and the E mobility will strengthen this trend because the need for even lighter construction will become more important. Quality requirements for the material are, therefore, becoming more important. For this study, billets of alloy EN AW-5083 were cast in the R&D casting pit at the TRIMET site in Essen. The hydrogen content in the molten aluminium was measured using, Hycal and Reduce Pressure Test devices. To test the hydrogen content in solid form, samples were taken from the billets and tested with a Leco RHEN 602 Hydrogen instrument. The purpose of the measurements was to compare the results of the readings and to investigate the influence of the casting parameters on the hydrogen content. The automotive sector is particularly important for the aluminium industry, and the E mobility will strengthen this trend because the need for even lighter construction will become more important. Quality requirements for the material are, therefore, becoming more important. For this study, billets of alloy EN AW-5083 were cast in the R&D casting pit at the TRIMET site in Essen. The hydrogen content in the molten aluminium was measured using, Hycal and Reduce Pressure Test devices. To test the hydrogen content in solid form, samples were taken from the billets and tested with a Leco RHEN 602 Hydrogen instrument. The purpose of the measurements was to compare the results of the readings and to investigate the influence of the casting parameters on the hydrogen content.

In the former EU-supported 4th framework programme EMPACT several large ingots were cast and characterized including detailed mapping of the chemical composition in different cross sections of the ingots. At the time of the project we did not have the modelling tools to support the measurements regarding the understanding of the different mechanisms involved in creating macrosegregation on large dimension ingots. Now, using a model specifically developed for DC-casting—Alsim, we have simulated two of these ingots cast at the research facility in Bonn. One of the ingots was grain refined—the other not. The metal distributor (combo-bag) for the non-grain refined ingot was later removed. The three different cases experienced distinctly different macrosegregation patterns and the mechanisms behind these patterns are discussed with the help of the simulation results.

In order to achieve a high quality aluminumAluminum ingot, fine grains are required. The electromagnetic stirringElectromagnetic stirring process is known as one of the processes that promotes grain size refinement in aluminum alloysAluminum alloys . In this study, a reversing Rotational Magnetic Field (reversing RMFReversing RMF ) that reverses the rotation direction of the electromagnetic field at regular intervals was applied to molten aluminumAluminum in the cylindrical container of a round billetBillet for DC castingDC casting . The molten aluminumAluminum underwent a clockwise and counter-clockwise flow by applying a reversing RMFReversing RMF . When the periodic time of the reversing RMFReversing RMF is long, the grain size of the billetBillet was finer than that of the mono-directional rotational flow. On the other hand, the grain size of the billetBillet center was not fine when the periodic time of the reversing RMFReversing RMF was short. The flow field was calculated by a CFDComputation Fluid Dynamics (CFD) Modeling simulation for comparison with the experimentalExperimental results. It was found that the development of the flow field affected the grain size refinement.

The Kozeny-Carman relationship is a widely acknowledged analytical modelModel that describes the permeability of porous structures using structural parameters. This modelModel is applied frequently to DC castingDC casting simulations and descriptions to describe the hot-tearing sensitivity of the mushy zoneMushy zone . Often, the structural parameters used in the Kozeny-Carman expression are difficult to obtain and uniform values are applied for a variety of castingCasting conditions. However, changes in fluid flow within the molten pool with all other castingCasting conditions identical can significantly alter the microstructureMicrostructure , and thus the permeability of the mushy zoneMushy zone . In this study, we perform a set of stirringStirring experiments using a standard DC castingDC casting setup, which demonstrate the relative importance of not only the grain size, but also the grain morphologyMorphology in decreasing the hot-cracking sensitivity of cast aluminumAluminum products.

Shrinkage induced flow, thermo-solutal convectionConvection and equiaxed grain motion are the major transport mechanisms contributing to macrosegregationMacrosegregation formation in aluminum alloysAluminum alloys produced through Direct Chill castingCasting . ExperimentalExperimental and numerical studies were conducted to provide insight on macrosegregationMacrosegregation formation in AA5182 ingots. Previous numerical studies indicated that the weak thermo-solutal convectionConvection , both individually and in its interaction with grain motion, has an insignificant contribution to macrosegregationMacrosegregation formation. These studies were, however, conducted using 2D simulations of sheet ingots. In this paper, we carry out 3D modelling of sheet ingots with the same alloyAlloy by employing a multiphase, multiscale solidificationSolidification modelModel based on volume averaging method accounting for thermo-solutal convectionConvection and globular grain motion. We show that the coupling between thermo-solutal convectionConvection and grain motion is important to provide a better description of macrosegregationMacrosegregation formation during DC castingDC casting of AA5182 alloyAlloy . The numerical work is discussed considering experimentalExperimental horizontal macrosegregationMacrosegregation maps.

The purpose of the present study was to investigate the effect of different grain refiners’ additions on structure and electrical conductivityElectrical conductivity of commercially electrically conductive (EC) grade 1370 aluminium alloyAluminium alloy . A series of controlled lab scale experiments were carried out by addition of 0.1 wt% AlAl -5Ti-1B, AlAl -3Ti-1B, OPTIFINE, TiBloy, and AlAl -3Ti-0.15C, grain refiners to molten aluminiumMolten Aluminium at 730 ± 5 °C. The macro structural analysis showed that 0.1 wt% of TiBloy, AlAl -5Ti-1B, AlAl -3Ti-1B, and OPTIFINE did not grain refine commercial EC grade aluminiumAluminium . The AlAl -3Ti-0.15C master alloyAlloy showed, however, good grain refiningGrain refining performancePerformance , giving an equiaxed structure. Fading effect was observed in the samples grain-refined by AlAl -3Ti-0.15C master alloyAlloy . The electrical conductivityElectrical conductivity of all the grain-refined samples decreased between 0.02–0.75 ± 0.3% IACS, compared to the reference samples of commercial pure aluminiumAluminium . However, the electrical conductivityElectrical conductivity increased slightly by holdingHolding the melt, after the addition of the grain refiners, for 90 min, that might be due to settling of the particles by grain refiner additions.

AlMg alloys are known to suffer from problematic oxidationOxidation that can result in significant dross formation and loss of Mg from the melt. Historically, beryllium has been used to minimize the oxidationOxidation as it forms a protective BeO layer at the oxide-metal interface that inhibits further oxidationOxidation of the Mg. Alternative protection agents to beryllium are desired due to its strong negative health impacts. The purpose of this paper is to summarize findings in respect to the effectiveness of CO2 cover gas and yttrium additions as alternatives to beryllium; by examining the rate and product of oxidationOxidation using thermogravimetric analysisThermogravimetric Analysis , electron microscopy and EDS. It was found that additions of as little as 5% CO2 to air atmosphere can reduce the oxidationOxidation of a 5% Mg alloyAlloy to nearly the same extent as beryllium additions, while the addition of 100 ppm of yttrium was found to have a limited impact on the oxidationOxidation .

The presence of non-metallic inclusions in aluminiumAluminium has become a more critical issue with increasing demands on surface quality and low final wall thicknesses of products. AluminiumAluminium carbide particles form during the primary aluminiumAluminium production due to the contact between aluminiumAluminium and carbon/carbonaceous species in the electrolysis cellElectrolysis cell . These particles are typically very small (<3 μm), however, they may have crucial impacts on the mechanical and optical properties of products when they agglomerate due to poor wetting/high surface tensionSurface Tension with/in aluminiumAluminium melts. The carbide concentration is typically reduced after metal re-meltingMelting . The current paper experimentally examines this concentration change and the measured effect of re-meltingMelting temperature, atmosphere and rate of carbide reduction during holdingHolding of the liquid metal. The study showed that electrolysis metal, initially containing approximately 35 ppm AlAl 4C3, retained carbide contents after re-meltingMelting in aluminaAlumina crucibles at 700, 750 or 800 °C at similar levels (2–12 ppm) as previously reported as corresponding to carbon saturation in the melt. The study also illustrated that the carbide level is rapidly decreased during re-meltingMelting , and that the reduction is faster in air than in argon, suggesting that the removal takes place via direct oxidationOxidation of carbide particles close to—or at the melt surface.

Ceramic Foam FiltrationFiltration (CFF) is a widely used technique to remove inclusions from AlAl melt. To ensure sufficient inclusions in the melt during the grain refiners/filtrationFiltration interaction, inclusion additionInclusion addition methods, such as chips addition, powder addition, mechanical stirringStirring , and wet up-gassing have been studied in this work. It is found that the addition of oxide causes the formation of irregularly shaped micropores in the cast samples. Chip addition is simple to conduct, introducing large amount and size of oxide film contaminationContamination . The 6061 alloyAlloy chips were more helpful for inclusion contaminationContamination than that for commercial purity AlAl chips. This is due to the improved wettabilityWettability by magnesiumMagnesium (Mg) content in the chips. The addition of oxide powder is difficult due to the poor wetting between oxide and AlAl matrix. Vortex created by mechanical stirringStirring and pre-treatment of the powders improved the powder addition significantly. Wet up-gassing introduces pores and a large amount of dross based on the flow rate of the Ar gas.

HydrogenHydrogen solubility is much higher in liquid than in solid aluminiumAluminium . Therefore, if the hydrogenHydrogen concentration in liquid aluminiumAluminium is too high prior to solidificationSolidification , there is high risk of gas porosityPorosity formation during the solidificationSolidification . In a gas or oil fired reverberatory furnaceFurnace for aluminiumAluminium , combustionCombustion produces large amounts of water vapourWater Vapour . The water vapourWater Vapour may react with aluminiumAluminium forming aluminiumAluminium oxide and hydrogenHydrogen gas. This hydrogenHydrogen gas is then the main source for hydrogenHydrogen in molten aluminiumMolten Aluminium . MeasurementsMeasurements of both water vapourWater Vapour in the furnace atmosphereFurnace atmosphere (combustionCombustion off-gas) and dissolved hydrogenHydrogen in the melt are presented. The measurementsMeasurements are compared to a modelModel for hydrogenHydrogen concentration in aluminiumAluminium as function of the measured water vapourWater Vapour concentration. It is concluded that H2O reacts with aluminiumAluminium to H2 and AlAl 2O3. 49% of this H2 escapes from the interface to the bulk gas phase, and 51% acts as a source for dissolved hydrogenHydrogen in the melt.

We report on the development and testing of a miniature vacuum degassing system designed for use in ladles, troughs, and furnaces. The system also generates an inert gas flow that can blanket the molten metal surface, thus degassing and preventing the reintroduction of hydrogen into the newly refined metal.

Melt cleanliness is essential for high quality aluminum production. The main cleanliness criteria are the content of dissolved hydrogen as well as the content of non-metallic inclusions. The latter may impair the castability of the aluminum melt as well as the mechanical properties and the machinability of the aluminum castings. A simple and efficient way to remove non-metallic inclusions is the application of filters during the casting process. The influence of the filter roughness on the filtration is undisputed but experimental proof is still pending. Filters with three different levels of roughness were subjected in filtration trials in a filtration pilot setup at Hydro (Bonn, Germany) allowing determination of the inclusion removal efficiency by the application of two LiMCA devices. In addition to the LiMCA measurements, PoDFA, Alscan measurements and investigations of the casted aluminum were done.

Although it is undisputed that the filtration of aluminum melt inside ceramic foam filters is influenced by the wetting behavior between the liquid melt and the material of the filter coating, experimental proof is still pending. For the present study, the contact angle of an AlSi7Mg alloy on substrates made of Al2O3, MgAl2O4, 3Al2O3·2SiO2 and TiO2 was measured by the sessile drop method at 730 °C using non-contact heating and capillary purification technique. The contact angles were compared with filtration efficiencies of filters with identical coating composition measured during filtration trials performed at a pilot casting line. For inclusions smaller than 110 µm, a correlation between contact angle and filtration efficiency was observed. Furthermore, adhesion forces of alumina inclusions on the four coating materials were experimentally determined using atomic force microscopy in a water-based model system. For inclusions larger than 70 µm, the filtration efficiency correlates with the measured adhesion force.

Non-metallic inclusions such as oxides, borides and carbides in aluminium melts are a major cause of product failure during both processing and use. To remove these inclusions, molten aluminium is usually filtered through a mechanical filter such as deep bed-filter, ceramic foam filter or Bonded Particle Filter (BPF). In this study three BPF from Pyrotek have been tested at Hydro’s reference centre in Sunndalsøra. The filters had different grit sizes; 6, 10, and 14 (equivalent to 30, 50, and 70 ppi). The filters were mounted in the patent pending Drain Free filter box developed by Hycast. LiMCA was used at the up-stream side of the two coarsest filter (Grit 6 and 10) and both up-stream and down-stream for the finest filter (Grit 14). Three samples from each of the filters have been studied in a light microscope, and inclusions have been counted using image analysis. In addition, PoDFA samples from the test with the finest filter were also analysed and discussed.

The filtration efficiency of Ceramic Foam Filters (CFFs) of grades 50 and 65 has been quantitatively evaluated using a hydraulic water system. Distilled water seeded with Polystyrene Microsphere particles with a distribution of 20 and 50 µm. The polystyrene particles were illuminated during the filtration step by a continuous laser sheet placed before and after the filter. Images of the illuminated particles were acquired, and their number automatically distinguished and counted by the use of the image processing software. The filtration efficiency was further calculated based on the ratio of counted particles before and after the filter. Based on the obtained results the potential of the present method is discussed for evaluating the filtration efficiency of CFFs as the filtration media for molten aluminium.

Hydro and Hycast have significant experience in using underpressure to lift liquid metal up from the level in the launders for metal refining and thereby avoiding drainage metal at the end of the cast. This is also utilized in the Drain Free Filtration (DFF) technology, a new Ceramic Foam Filter (CFF) technology that has been developed. Eliminating drainage metal is a cost factor as well as an advantage regarding safety. In a standard CFF box the metal flow direction during priming is the same as during filtration. With the DFF technology the filters are primed in the reverse direction, which gives several advantages when it comes to how well the priming is working and for the subsequent filtration efficiency. Tests with a prototype DFF box with 23″ filters have shown that priming of 80 ppi filters is working very well. Thus, the new technology will enable Hydro to produce high quality metal for critical products that will help our customers.

Inclusions are one of the most serious problems encountered in aluminium production and melt treatment. Even small inclusions, not larger than a few tens of micrometres, can potentially have considerable consequences for the down-stream processing and a detrimental effect on the final product. Ceramic Foam Filters (CFFs) are commonly used to remove inclusions from the melt before the casting process. The very first phase of the filtration is called the priming period. This is when the molten metal meets the filter and fills up the pores inside the filter. In order to obtain good priming and to avoid freezing of the metal inside the filter, the filter must be properly preheated. During standard operation in industry, the metal flow direction during priming is typically the same as the metal flow during filtration. In the present work, equipment for testing the effect of reverse priming has been developed. Tests with standard and reversed priming directions have been carried out and the spent filters have been examined. The interface between the metal and the filter has been studied and it is concluded that all filters were well primed no matter the priming direction.

The estimation/measurement of the concentration and size distribution of particles/inclusions/intermetallics in aluminum melts is critical for high-end aluminum products, especially for automotive and aerospace applications. To meet future challenges, particles/inclusions of less than 10 µm in diameter need to be distinguished. Established methods such as the Liquid Metal Cleanliness Analyzer (LiMCA), Porous Disc Filtration Apparatus (PoDFA), or K-Mold have all their limitations, and are neither cost- nor time-efficient. In the present work computational algorithms for automated image acquisition and processing have been developed, tested and further optimized. A Matlab implementation is used for the processing, control and data management of the automatically acquired micrographs, while contrast enhancing functions and geometrical operations are used to identify the particles. The code is benchmarked by replicating manual counts of the same images down to a particle diameter of 5 μm.

Recent work on the casting of thin, wider sheets of aluminum alloys on the Horizontal Single Belt Caster (HSBC), has once again confirmed the viability of this casting process to deliver liquid metal of thicknesses ~5 mm, or less, onto a moving water cooled belt, in an iso-kinetic manner. For this, the speed of the liquid metal delivered across the width of the belt, must quickly match that of the water-cooled moving belt, whilst avoiding potential backflows and hydraulic jumps. The caster, now operating at MetSim Inc. is producing strip widths up to ~250 mm. As for the 100 mm wide strips cast in the past, the newer samples produced were improved in terms of uniform cross-sectional thickness, possessing good, top and bottom, quality surfaces, with straight edges. Compared with yields of ~65% for Direct Cast (DC) sheet material, for this HSBC sheet yields approach ~100%, without any need for side dams, or electromagnetic braking. The success of the present system relies on sophisticated metal flow management, in the presence of relatively rapid, unconstrained, solidification. This results in uniform, fine-grained, microstructures of aluminum alloys, free of any macro-segregation, macro-porosity, or surface blemishes, with equivalent metallurgical properties to those of the DC cast material. As such, downstream processing steps to final product are significantly reduced, with attendant cost savings, whilst capital costs for a full-scale system are relatively inconsequential, versus equivalent DC costs.

The productivity of the twin roll casting process has been largely limited by the heat transferHeat transfer capability of the steelSteel shells used on the caster rolls. Increase the casting speedCasting speed to improve steelSteel shell roll caster productivity can lead to casting conditions which generates casting surface and internal defects (heat lines, central line segregation). Roll caster productivity improvements can be achieved by replacing steelSteel shell with copper alloy shell to take advantage of the higher thermal conductivityThermal conductivity of copper relative to steelSteel , which provides an increased cooling capacity of the working rolls. The paper presents specific quality aspects which must be consider in the case of one copper shellCopper Shell roll strip castingStrip Casting of 1050 alloy. The quality aspects are the as cast strip surface topography which is direct related with final gauge surface cleanliness and final gauge rolled material grain structure and mechanical propertiesMechanical properties .

Microstructural features of twin-roll castTwin-roll cast aluminumAluminum products are strongly affected by the parameters of the castingCasting process. Among these parameters, strip thicknessStrip thickness is one of the most critical ones which dictates the solidificationSolidification process and directly affects the microstructureMicrostructure and the quality of the as-cast sheet surface. In this study, 8xxx (Al-Fe-Mn) alloys were cast with different strip thicknesses via an industrial scale twin-roll caster and it was aimed to elucidate the effect of the strip thicknessStrip thickness on secondary phases and grain structures along with the formation of macro-segregations. Microstructures of the samples were investigated by employing metallographic techniques. Complementary studies were performed by tensileTensile tests, electrical conductivityElectrical conductivity and micro hardnessHardness measurementsMeasurements . Results show that the strip thicknessStrip thickness is an important tool to obtain desired properties in as-cast materials.

In this study, the effect of homogenizationHomogenization heat treatment on precipitationPrecipitation and recrystallization kinetics as well as geometry of recrystallized grains during subsequent annealing of direct chill cast hot rolled and twin-roll castTwin-roll cast AA 3105 strips was investigated. For this purpose, homogenizationHomogenization heat treatment was conducted on AA 3105 strips after cold rolling with an equivalent strain of 0.66. Homogenized and non-homogenized strips were then cold rolled with an equivalent strain of 1.06. Results reveal that homogenized twin-roll castTwin-roll cast AA 3105 strip exhibits lower recrystallization temperature as compared to that of non-homogenized one and finer as well as quasi-equiaxed grainsEquiaxed grains through particle-stimulated nucleationNucleation mechanismMechanism after soft annealing. On the other hand, for direct chill cast hot rolled AA 3105 strip, homogenizationHomogenization heat treatment leads to lower recrystallization kinetics.

HoldingHolding furnaces use less energyEnergy than meltingMelting furnaces but still represent an important process to optimize in the aluminumAluminum industry. Given that less energyEnergy is used, low-cost changes are needed to cost justify any furnaceFurnace or burner work. Further modelingModeling on a holding furnaceHolding Furnace was done to examine and investigate the optimum design to reduce energyEnergy usage. This paper investigates different options, e.g. burner size and load, chimney location and height, and furnaceFurnace length and height. Preliminary results indicated a significant increase in the exergy efficiencies and therefore gas saving when the optimum selection of burner size, chimney location and furnaceFurnace length/height is considered.

MeltingMelting and recyclingRecycling of AlAl alloys involve large amounts of energyEnergy and CO2 release. In order to minimize energy consumptionEnergy consumption and environmentEnvironment impact, a novel approach has been developed and tested for this industrial sector, but it can be extended to other processes and materials. The approach is based on on-line data acquisitionData acquisition and efficient numerical modelingModeling of heat exchanges within a meltingMelting furnaceFurnace . The fast and efficient numerical modelNumerical Model , which includes the physical mechanisms of combustionCombustion , radiationRadiation , conductionConduction and convectionConvection , has a few adjustable parameters which are calibrated on-line by a few data acquisitionData acquisition values. A friendly user-interface allows furnaceFurnace operators to monitor the meltingMelting process and optimize mass loading, door opening, heating sequences, etc. The main features of this tool are presented.

Challenged with responding to increased market demand, key priorities for secondary aluminumSecondary aluminum smelters today are improving scrapScrap recyclingRecycling efficiency, while reducing emissions. Moreover, due to rising scrapScrap prices, secondary aluminiumAluminium recyclers are turning to various qualities of scraps—even with high contents of organic materials. To address these trends, Air Liquide has recently carried out developments of an advanced control (BoostAL COntrol) which quickly detects peaks of combustibles in the fumes and reduces fuel consumption by recovering energyEnergy from volatile organic compounds in the scrapScrap , along with an improved oxy-burner technologyTechnology (BoostAL DDC) which optimizes heat transferHeat transfer during the different phases of the melt process through two additional types of combustionCombustion modes. This paper will describe an industrial case study where BoostAL DDC has been combined with BoostAL COntrol for meltingMelting both clean scrapScrap and contaminated scrapScrap , allowing one to increase productivity and reduce specific energy consumptionEnergy consumption while keeping high metal yield.

Electromagnetic (EM) fields can have a significant influence on the behavior of molten aluminumAluminum and its alloys, and are today used to pump, circulate and transfer metal using Electro Magnetic Pumps (EMP) or to homogenize the metal in the furnaceFurnace using Under Floor Stirrers (UFS). The present paper discussed the newly developed Electromagnetic Transfer and Circulation (ETAC) system, which applies the same fundamental physics. A unique characteristic of the ETAC, is that it combines the lower turbulence of the UFS with the high throughput of the EMP. This gives a large volume stream of metal (adjustable until up to 20 t/min) during circulation, alloying, homogenizationHomogenization and transferring metal. It also secures a lower surface/dross entrainment. The ETAC is fully adjustable in power and thrust ratios with less slip, making it suitable for almost all furnaceFurnace operations and alloys at fairly low metal levels in the furnaceFurnace .

Electromagnetic stirringElectromagnetic stirring (AL-EMSEMS ) for aluminium is now a well-established technology used to enhance chemical and thermal homogeneity and reduce both cycle time and dross formation for meltingMelting and holding furnaces. This paper will discuss how AL-EMSEMS stirringStirring profiles can be optimizedOptimized utilizing data from the furnaceFurnace with the aim of fully automating its operation and access further improvements in electrical consumption and quality in the aluminium melt. In addition, this paper will discuss how alloying practices can be improved using full power stirringStirring in holding and meltingMelting furnaces.

Calcined Petroleum CokePetroleum coke CPC of 75% passing 75 µm is typically mixed with pitchPitch to form the anodes. Some paste plants have their reasons to use super fine ground dust, like 75% passing 32 µm. Claudius Peters EM-Ball-Race-Mills BRM can manage such high fineness with thorough following of experience and scientific grindingGrinding tests in industrial size air swept mills. Test on an industrial scale equipment has been carried out for verification. The changes in power consumption and in iron contamination with the different settings have been investigated. The results are presented. An increase in specific power consumption, in specific iron contamination and a decrease in throughput could be observed with a given equipment. GrindingGrinding is a challenge but follows physical rules, which are easy to understand, when the necessary test equipment is available.

In recent years, anode property optimization has mainly been obtained through dry mix, mixing or forming process improvements. Another way to improve anode properties is to work on raw materials and study the ability of coal tar pitch to coat and penetrate coke porosities. To validate the use of a new binder, it is important to understand the chemical and physical interactions that occur when coke grains meet liquid pitch. Fives has developed a laboratory-based method to characterize pitch/coke interaction. Its principle is based on the dynamic penetration technique of sessile drops. Complex phenomena due to the porosity of the coke and the chemical composition of the pitch lead to the use of a fluid/substrate model to dissociate the physical and chemical interactions. This article summarizes the approach for characterizing pitch imbibition on porous coke medium. This is a first step to predict anode performance using different grade of pitch.

A crack-resistant carbon anode in high-amperage aluminium cells contributes to improved cell stability and reduced operational costs. Increased metal production by current increase programs is less challenging, and energy savings by deeper anode slots are possible. As an effort to search an improved guidance in the anode manufacturing process and in the raw material selection, new and modified physical quality parameters, based on physical loading tests and finite element analysis, are introduced. Namely, an improvement to the measurement of fracture toughness along with new parameters characterizing the non-linearity in observed stress-strain curves are presented. A cooperation between Itasca Consultants and Hydro has been established to develop a particle-based model using the Discrete Element Method, aiming to study the relationship between the microstructure and the macroscopic mechanical properties and quality parameters of the carbon anode. The model is being developed in the software PFC2D 5.0 (Particle Flow Code) from Itasca. The model is applied to study the origin of the experimentally observed non-linearity in mechanical tests.

The application of vacuum during forming was first introduced to anode manufacturing in the early 1970s. Using vacuum has become quite widespread more recently since it allows anodes to be formed at higher temperatures with a lower risk of cracking, thus helping to increase anode density and improve other related properties. As a part of a larger anode project, the two vibroformers in Emirates Global Aluminium’s Jebel Ali Paste Plant were upgraded with the addition of vacuum units. These retrofits gave the opportunity to study the impact of forming under vacuum in the green and baking stages of anode production. This paper summarizes the key lessons learnt on how vacuum forming affects green and baked anode properties and the process changes made to take advantage of the higher densities achieved with vacuum while maintaining good anode electrical resistivity.

Consistent and high anode quality is a key when smelters look for continuous economical and operational performance. Resulting from complex and long processes with various influent factors, anode quality deviations are difficult to anticipate in real-time, or to qualify when they start to destroy value on the pot. To address this problem, continuous and real-time anode quality monitoring solutions emerged recently as part of the digital revolution. To be efficient, such solutions must include a reliable anode tracking system. This paper presents a new vision-based anode tracking system. Using digital signature of the anode, like for a fingerprint, the solution went through a successful proof of concept at Aluminium Dunkerque carbon plant. Hundreds of anodes from cooling tunnel down to rodding shop, passed through several vision-based identification stations to evaluate the anode identification rate. This solution is part of a global Carbon Material Tracking and Process Optimization system.

AluminiumAluminium producers are constantly facing challenges regarding the increase in production costs including those related to coal tar pitchCoal tar pitch (CTP). CTP is used as binder to produce carbon anodes. Alternative sources to CTP capable of addressing the cost and health issues without decreasing anodeAnode quality, are thus of great interest. Bio-pitches, produced from bio-oils, could be a good candidate in this regard. The objective of this study is to characterize bio-pitchBio-pitch , obtained from different origins, and to reveal its potential as an alternative for CTPCoal tar pitch in anodeAnode production process. Three bio-pitches were produced from different bio-massBio-mass sources under the same pyrolysis conditions. Both physical and chemical properties of bio-pitches were characterized, such as density, softening point, coking value, quinoline insoluble, molecular weight, viscosity, chemical groups and surface composition. The microstructures of the three bio-pitches were also compared to that of CTPCoal tar pitch .

The MONSOON projectThe MONSOON project is a European H2020 innovation project dedicated to optimize process industry through resources and energy efficiencyEnergy efficiency . The consortium is composed of 11 partners from 7 European countries. Rio Tinto and AluminiumAluminium Dunkerque (AD) are among the industrial partners, while ProbaYes acts as Data Science experts. The MONSOON projectThe MONSOON project has built a two-components platform dedicated to both development and deployment of data analytics functions, employed for AD’s Paste Plant process optimizationOptimization . The carbon anodes are a key component to the electrolysis reaction. The quality of the anodes (density, composition…) directly impacts the quantity and quality of the produced aluminumAluminum . A method, based on machine learningMachine learning techniques, has been developed for monitoring the quality of the produced anodes and understanding the root causes of non-quality, using real-time Paste Plant data. This article presents the approach proposed in this context, the designed tools, and the first results obtained so far.

The quality of cokeCoke materials available for anodes for the aluminium industryAluminium Industry is changing and industrial cokes with higher impurity levels are now introduced. The cokes in the anodes must meet specifications with respect to impurity levels to ensure proper operation in the electrolysis cells, and a desired quality of the aluminiumAluminium metal. The presence of sulfurSulfur has been observed to reduce the CO2 reactivity and a certain level of sulfurSulfur is therefore targeted in the anodes. In this work, the significance of varying sulfurSulfur and metal impurity content in industrial cokes were evaluated with respect to CO2 reactivity, accessible surface area, pore size distributionPore size distribution , surface oxide groups and crystallite reactive edge planes. While relatively similar cokes are observed to give a lower reactivity with increasing sulfurSulfur content, cokes that have distinct differences in surface properties can have dissimilar reactivity despite identical sulfurSulfur content. Correlations between pore size distributionPore size distribution and presence of S-S bound sulfurSulfur , possibly condensed Sx, was also observed.

Anode bakingAnode baking furnaces are a key component of the manufacturing process of prebaked anodes used for aluminiumAluminium production. Green anodes are loaded into pits before being submitted to high temperature in order to meet resistivity and chemical reactivity specifications. These pits are separated from each other by fluewalls and headwalls made of dense refractory material. In order to answer to the need for productivity increaseProductivity increase and cost reductionCost reduction , a new generation of design for baking furnaceBaking Furnace without headwalls has been developed. From the proof of concept and the first tests realized in Rio Tinto AluminiumAluminium Grande Baie plant (UGB) to the industrial prototype implemented at Bell Bay AluminiumAluminium (BBA), this paper presents the different phases undertaken to successfully develop and test this breakthrough technologyTechnology . The adaptations made to the operation sequences and the specific tools used to operate the industrial prototype will be described as well as the performance achievedPerformance achieved to date at the two sites. Finally, the paper concludes with a summary of the benefits of this technologyTechnology depending on the scenario of implementation on greenfield or brownfield projects.

Anode baking is the most critical and expensive step in carbon anodeCarbon anode manufacturing process. Therefore, more focus is required towards a safe baking process to achieve best product quality and optimizedOptimized cost. The baking of anodes is a process where combustible substances are released. So there is high risk of fire and explosion in ring main duct of furnaceFurnace and in fume treatment center. Modern baking furnaces are of open-type ring furnaceFurnace with indirect heating of anodes in the absence of air. The risk associated at different stages of baking process and its consequences can be evaluated for the protection of operating personnel and furnaceFurnace equipment. Such risk assessment study can be done for existing furnaces as well as new furnaces to be constructed. This paper will present and discuss the various causes of fire incident/explosion in furnaceFurnace and how operational practices and safetySafety systems can reduce the occurrence of fire incidents. Protection devices available in ABF at Aditya Aluminium (unit of Hindalco Industries Ltd.) and the existing operational practices to be carried out by ABF manager to minimize the losses are presented.

To become a world-class company, INALUM should increase its competitiveness, and one of the strategies is reduction of production cost. AnodeAnode production cost is one of the largest cost contributors for aluminumAluminum production. In such a way the optimizationOptimization of soaking time was applied by using baking curve of fire progression (FP) 30 h instead of the curves of FP 32, 34 and 36 h. By this method and based on actual data, including measurement of anodeAnode temperature, fuel consumption reduced by 5.05 L/ton Baked Block (BB) which leads to saving of fuel consumption of up to 578 m3/year while still maintaining good anodeAnode quality. Moreover, it could improve the effectiveness of pit cover change duration from 15 to 10 min (33%) and it was simultaneously reducing the generated CO2 emission up to 9.3 kg (7.7%) due to reduced fuel consumption.

Real density (RD) and crystallite size (LC) are common measures to control coke calcination levels. They are also measured routinely on anode core samples as a means of trackingTracking anode baking levels. Many anode producers target anode RD levels which are at least 0.02 g/cm3 higher than the calcined petroleum cokePetroleum coke (CPC) RD to minimize differential reactivity between the CPC and binder derived carbon. Depending on the calcining process parameters and technology, coke RD and LC can vary significantly. Shaft CPC often shows a higher RD and LC than rotary kiln CPC due to the longer residence times. Coke blends with CPC having different RD and LC values are now regularly used by aluminum smelters. This paper reports on the results of pilot anode studies to evaluate the impact of the starting CPC RD and LC on final anode RD, LC and other properties such as specific electrical resistivity and carboxy reactivity.

The present work has recently been accepted for publication in Metallurgical and Materials Transactions B. An extended abstract is presented here to give the reader an overview of the content of the published work.

Micro X-ray Computed TomographyX-Ray Computed Tomography (CT) is an instrumental method for recording inner structure 3D images without damaging the observed volume. A methodologyMethodology has been developed by SINTEF for CT of carbonaceous materials, yielding detailed structural views and quantification of the pore, void and grain distribution within volumes of 10–130 mm diameter. Example results are shown from a study of anodeAnode anisotropyAnisotropy . A series of vertical cores from a prebaked anodePrebaked anode was analysed, selected due to clear difference in top, middle and bottom level structure. The CT data was calibrated and connected to the physical position in the anodeAnode . The data was analysed with various methods that quantify the degree of anisotropyAnisotropy . The analysis show that the anodes have a 10–15 cm wide zone of high anisotropyAnisotropy , while the top and bottom of the anodeAnode are more isotropic. Some possible reasons for mid-height anisotropyAnisotropy are discussed.

High sulfurSulfur petroleum cokes were calcined in a high temperature furnaceFurnace to reduce the sulfurSulfur content 9 during the prebaked anodePrebaked anode production, and that can be good for reducing environmentEnvironment pollution. The preparation test and performancePerformance analysis of anodes were carried out. The ways of injecting the desulfurized cokeCoke and its influence on quality of the anodeAnode are discussed. The results show that although the high temperature treatment greatly reduces the sulfurSulfur content of the high-sulfurSulfur petroleum cokePetroleum coke , it has a negative effect on the microstructureMicrostructure and properties of the anodeAnode , and the desulfurized cokeCoke cannot be used to product anodeAnode in large quantities. A certain proportion of the desulfurized cokeCoke can be used with little effect on the anode propertiesAnode Properties . The present work can provide a reference for the applicationApplication of high temperature desulfurized petroleum cokePetroleum coke in anodeAnode production.

Anodes fabricated from a single source coke were used for investigations of effect of porosity and surface roughness on the electrochemical performance in laboratory scale cells. In order to fabricate anodes differing in porosity, the production parameters were varied with two levels of mixing temperatures (150 and 210 °C) and three baking levels (underbaking at 1150°E, normal baking at 1260°E, overbaking at 1350°E). °E denotes the equivalent temperature which is a function of both the temperature the anode sees, and the time kept at this temperature. The low mixing anodes were more inhomogeneous with respect to both micro- and macroporosity, which can be attributed to the wetting between pitch and coke. After electrolysis, the real surface area of the low mixing anodes was about 13% higher than the high mixing anodes. Also, the low mixing electrodes had slightly larger electrochemically active surface area after electrolysis compared to the high mixing electrodes, as evidenced by higher capacitance measured at low current densities. Still, the mixing and equivalent baking temperatures did not affect the electrochemical overpotential at 1 A/cm2 to any significant extent. This could be understood from the 3D computed tomography images, which also showed that the electrolyte does not generally penetrate into the pores on the surface, penetration will depend on the size and shape of the pore.

Autopsies of six spent potlinings with different carbon cathode block grades, amperage regimes and cell technologies were conducted at three separate smelters to reveal possible mechanisms causing cathode wear. Microstructure of the cathode samples from the autopsies was investigated by optical and electron microscopy and X-ray computed tomography, while the composition of solid bath at the surface and in the interior pores were investigated by X-ray diffraction and electron microscopy. NB: This is an extended abstract of an article to be published in JOM with the same title.

The uniaxial compressive creep tests for graphite cathode samples under 4 MPa constant loading have been carried out by a modified Rapoport-Samoilenko apparatus. Experimental results have been obtained for different temperatures (920, 940 and 960 °C) under both laboratory aluminum electrolysis and non-electrolysis conditions. The results indicated that the creep strain of graphite samples increased with higher temperature and electrolysis process. The compressive strength of the electrolysis samples decrease significantly (>10 MPa) compared to the non-electrolysis samples, when both have been subjected to creep tests under the same operating temperature. Some transverse cracks filled with fluoride species, extending from the contact interface of Al-cathode into the inner area of the electrolytic cathode, can be observed by SEM after uniaxial compressive strength tests. Creep-electrolysis induced cracks are also associated with reduced compressive strength. The observed results may provide direct evidence for better understanding of material deterioration and mechanical failures of the cathodes in aluminum electrolysis process.

Fe-TiB2 composite cathode materials were prepared by cold pressing sintering in which metal Fe was added as sintering aids. The electrolysis performance was studied in a 20 A electrolysis test, and the composition phase analyses of the composite cathode materials before and after the electrolysis test were carried out by using an energy spectrometer (EDS), and the migration behavior of various elements in the electrolysis process was studied. The results showed that the Fe could effectively fill the gap between the aggregate during the sintering process and improve the sintering density of the composite cathode material significantly. The voltage of the 20 A electrolysis test is stable. The impurity of the aluminum is 0.81%. The surface of the composite cathode is wetted obviously by the aluminum liquid. In the process of electrolysis, the alkali metal is main. In the permeation of the liquid electrolyte into the cathode material, the permeation of K element was more deeply than that of Na element; the Al produced on the cathode surface and the Fe in the cathode material will diffuse to each other until the relative equilibrium is reached.

Chromium oxide is considered as one of the candidate lining materials for low temperature aluminum electrolysis. The chemical properties of chromium oxide in KF-NaF-AlF3 based low temperature electrolyte melt were studied by means of static oxidation tests and electrolysis experiment with vertical inert anodes. The results showed that trivalent chromium oxide (III) could be oxidized to generate different valence states chromates (II, III, IV, VI) in electrolyte melt. Among them, the hexavalent chromates could be volatilized in large amount with electrolyte volatiles. The strength of the oxidizing atmosphere was the key factor affecting the generation of yellow hexavalent chromates which could be significantly reduced by the existence of protective atmosphere and graphite. Under the condition of electrolysis with inert anodes, there was not only the massive formation and volatilization of hexavalent chromates, but also the pseudo volatilization of chromium oxide (III) caused by hot-oxygen.

To facilitate continuous improvement and permit amperage increases in the pot room, efforts have been focused on anode formulation at ALUMINIUM ALMAHDI. The impact of finer finesFines on baked anode properties was considered and trials to measure this impact were developed. Green millGreen Mill operation and process parameters were adjusted to produce finer finesFines as measured by BlaineBlaine Number—the R&D Carbon method used to infer the “fineness” of carbon dust. Analyses were conducted on green and baked anode properties. Green and baked apparent density and air permeability improved with high statistical correlation. Electrical resistivity and flexural strengthStrength required increased pitchPitch content to demonstrate improvement. No crack rate increase was observed and the bake loss was very low. Finer finesFines are also a potential control for baked anode properties as calcined coke.

The demand for automotive sheet shows the highest growth rates in the aluminium industryAluminium Industry . Currently, the main alloys are from 5.xxx and 6.xxx series with a variety of approx. 40 different specifications. Such a mixed scrapScrap quality cannot be used in an efficient way in cast houses, due to the divergent Mg and Si concentrations. Additionally, the ratios between 5.xxx and 6.xxx scrapScrap are unpredictable. Today, the only technical possibility to distinguish between these alloys is sensor based sortingSorting using LIBSLaser induced breakdown spectroscopy (LIBS) . Such a sortingSorting machine has to produce two sortingSorting fractions, which both fulfill the requirements of the new wroughtWrought alloys. In this case a high sortingSorting efficiency is mandatory. First results show a purity of the sorted fraction above 95% as well as a high recoveryRecovery of the sorted material also above 90%.

AluminumAluminum is widely used in daily household consumable goods such as food and drink packaging materials, storage containers, etc. The disposal of such goods into household waste means that this waste stream contains a significant amount of aluminumAluminum . Domestic waste is commonly sent to incinerator plants where the organics are combusted while the metallic content stays in the bottom ashBottom ash , which is subsequently separated into various metal streams. Because of the importance of aluminiumAluminium in the circular economyCircular economy , there is a need for efficient recoveryRecovery procedures for this metal source. This paper discusses the recyclability and the recoveryRecovery rate of aluminumAluminum from the bottom ashBottom ash through remelting with a molten salt. The remelting experiments were performed under a 50–50 wt% NaCl:KCl mixture with a 2 wt% CaF2 addition to promote metal coalescence. The oxide thickness and trace element content of the starting metal and the composition of the resulting metal were characterized as these parameters largely determine the recoveryRecovery rate and recyclability of these secondary metal streams. The laboratoryLaboratory results showed the coalescence efficiency up to 99.5% and the material yield up to 92%. High deviation in oxide content based on the oxide layer thickness measurementsMeasurements was observed which crucially affects the metal losses in recyclingRecycling .

The Vertical Floatation Melter (VFD) has undergone pilot testing in removing organics from scrapScrap aluminumAluminum . The VFD uses a vertical cone in which the scrapScrap is dropped into the top and products of combustionCombustion at 1000 °F are introduced into the bottom, flowing countercurrent to the scrapScrap . The gases float the scrapScrap in the cone resulting in very high convective heat transferHeat transfer which leads to rapid decoating with minimal metal loss. Turnings, finesFines , Twitch, and UBC have been processed through a single unit. Decoating times are about 1 min. Measured energyEnergy use varies from 78 to 854 Btu/lbm; measured preheat temperatures are 850 °F. Decoat efficiency appears good with visually no oxidationOxidation present and no evidence of organics. Samples have been sent to a lab to confirm this.

RecyclingRecycling is a critical part of obtaining a more circular economyCircular economy . In the metals secondary industry, traditional equipment (a magnet, file, and/or grindingGrinding wheel) used to identify and sort materials at their end of life can aid in grouping metals (i.e. AlAl + Mg alloys, ferrous, high temperature alloys, etc.), but they are incapable of identifying the alloyAlloy ’s elemental composition; a necessity for preventing downcyclingDowncycling and maximizing secondary utilization rates. Handheld analyzersHandheld analyzers that utilize X-ray fluorescence (XRF)X-ray fluorescence (XRF) and spectroscopy (LIBSLaser induced breakdown spectroscopy (LIBS) ) technologyTechnology may offer technological assistance that is helpful for achieving this level of analysis, often referred to as Positive Material IdentificationMaterial identification (PMI). This work tests the performancePerformance of these units under the challenging conditions present in yards (contaminated, unpolished, rugged scraps). These instruments, with their increasing safetySafety settings, ruggedness, ease of point-click use and quick read times (for both XRFX-ray fluorescence (XRF) and LIBSLaser induced breakdown spectroscopy (LIBS) ) have significant potential, especially with ability to ID metal faster than cognitive recognition. Additionally, as unit costs of these instruments continue to decrease and the range of varying types of metal entering yards continues to widen, the return on investment becomes more immediate. However, extreme fluctuations of reported elemental compositions are being seen even when measurementsMeasurements have been taken in the same place consecutively; indicating that in their current state, they can inform content of material but aren’t necessarily reliable for reporting accurate and precise compositional percentages.

Emissions from the transportation industry combined with increasing consumption of materials have inspired the automotive industry to use lightweight materials in auto-bodies. A wide diversity of materials is being used, for example, aluminum, magnesium, and plastic composites. This light weighting approach is a proven sustainability strategy improving fuel economy and thereby reducing greenhouse gas emissions. However, increasing the number of differing types of materials in cars is actually complicating recycling operations. Critical metals used as alloying additions are dissipatively lost in the recycling process and can also negatively impact recycling rates by accumulating as tramp elements. This work combines compositional characterization of automotive materials, material flow analysis, and techno-economic assessment to better understand this problem and inform solutions. Results show that both technical solutions like sensor-based sorting and operational solutions like compositionally based blending can decrease material losses, thereby reducing the negative impacts and inching closer to a circular economy.

During the 1990s Powerball Industries, UT had demonstrated producing Hydrogen on demand machinery—where encapsulated sodium metal is reacted with water to release hydrogen gas under pressure. The hydrogen on demand has several applications. Here we discuss the ongoing research of making use of aluminum (recycled or newly produced) with anhydrous sodium sulfate—which will make sodium metal, sulfur oxides, and aluminum oxide. The thermodynamic analysis shows suitable physicochemical conditions for the reactions. Preliminary economics using aluminum scrap—recycled aluminum is shown.

The isothermal hot pressing (IHP) of skimmed aluminium dross, considered in this study, was performed under laboratory conditions using a cylindrical pressing model made from high-temperature stainless steel. The pressing model was inserted into an electrical furnace with a protective argon atmosphere. The temperature of the pressing was within the interval 650–900 °C, while the applied pressure varied between 5 and 50 bars. The laboratory results showed that when using IHP it is possible to reduce the remaining aluminium content in “pressed dross skulls” below 10%.

Scandium is a metal with emerging uses in aluminium alloying, lighting and ceramic fuel cell applications. In recent years, an increase in demand for scandium has been hampered by a lack of supply options. This has driven the development of several projects where scandium production is a major focus, in particular laterite sources in Australia, Turkey and the Philippines. Solvent extraction is commonly used for recovery of scandium from the laterite leach solutions. A number of chemicals are available for solvent extraction of scandium. This paper reviews the current available methods and recent adaptations of common processing solutions.

Global production of commercial scandium oxide currently produces only ~15–20 tonne per year. It is produced from tailings and streams of titanium and uranium industries and complies with high quality standards with Sc2O3 content ≥99.9 mass%. UC RUSAL has developed a technology for Sc2O3 extraction from bauxite residue that can provide for a substantial increase of Sc2O3 output making it a commodity product with low production cost. For the scandium concentrate obtained at RUSAL pilot plant (Sc2O3 content up to 52%) the purification technology was developed combining both well-known and novel methods like double hydrolysis and scandium precipitation in the form of complex compounds, i.e. double sulphate of scandium and sodium Na3Sc(SO4)35H2O. The process assures efficient removal of impurities (incl. Zr, Ti, Hf, Th, REM), low operation costs, minimal secondary losses of scandium, low amount of hazardous wastes and was successfully tested at lab and pilot plant scales.

ScandiumScandium is considered to be the best alloying metal for aluminiumAluminium . Aluminum-scandiumAluminum-scandium alloys are characterized by unique properties: high thermal and corrosion resistance, durability, superplasticity, self-hardening capacity, fine weldability, and have potential for applicationApplication in such industries as aerospace, automotive and shipbuilding. RUSAL has developed a series of technologies to promote wide applicationApplication of scandiumScandium alloys, including the environmentally and Bayer process-friendly technologyTechnology of scandium oxide extractionScandium oxide extraction from bauxite residueBauxite residue . This paper shows the results of research on scandiumScandium sorptionSorption from bauxite residueBauxite residue carbonation leachingCarbonation leaching solutions at laboratoryLaboratory and at pilot plant scales at one of Rusal’s aluminaAlumina refineries. Optimum conditions for sorptionSorption and desorption processes were defined not only assuring improved scandiumScandium concentrate quality but also allowing to obtain the lowest cost of scandium oxideScandium oxide as compared to other industrial scandium oxide productionScandium oxide production technologies.

A scandiumScandium rare earth ore belongs to the basic-ultrabasic rock mass, which is mainly composed of sulfide, carbonate, oxide, silicateSilicate , with silicateSilicate accounting for about 89% of the total mineral. However, it is very difficult to enrich this ore, because of the poor beneficiability of silicateSilicate and dispersed distribution of scandiumScandium minerals. This paper has focused on magnetic separationMagnetic separation processes for the pre-concentrationPre-concentration of poor magnetite associated with scandium oxideScandium oxide ore, according to the composition and occurrence state of scandiumScandium . The condition experiment indicated that appropriate magnetic field strengthStrength was 0.1 T in the low-intensity magnetic separationMagnetic separation process, 0.9 T in the high-intensity magnetic separationMagnetic separation process and 0.7 T in high-intensity magnetic scavenging process. At last, the open circuit experiment of whole beneficiationBeneficiation process based on the optimum parameters should be carried out, the separation indexes with scandiumScandium grade of 81.37 g/t and recoveryRecovery rate of 70.31 wt% were obtained.

The refinement of AlAl alloys has been extensively investigated for several decades both in industry and academia. However, the grain refinementGrain refinement potency by TiB2 alone is not high as expected. The presence of other solutesSolutes (e.g. Ti) is, therefore, of great necessity to enhance the grain refinementGrain refinement potency of TiB2 by tailoring the heterogeneous nucleationNucleation interface of TiB2. Furthermore, in order to further improve the grain refinementGrain refinement of AlAl alloys, Sc and Zr were also used together with TiB2. However, the addition of Sc with high concentrations is not affordable because Sc is very expensive for a large-scale applicationApplication in foundry industry. The main aim of this present investigation is to determine an optimum grain refiner for AlAl 4CuTi alloyAlloy by using Zr, Sc and Er because Er is less expensive than Sc. A combined addition of Zr and Sc was found to have a significant grain refinementGrain refinement effect on AlAl alloys rather than Zr or Sc alone, which can be interpreted by the fact that Sc is dissolved in AlAl 3Zr phase. In contrast to Sc, Er does not appear to act as an efficient grain refiner because AlCuEr phase forms which didn’t act as an active heterogeneous nucleationNucleation site and subsequently didn’t facilitate the grain refinementGrain refinement phenomenon. Finally, a combination of 0.002 wt% TiB2 together with 0.1 wt% Sc and 0.15 wt% Er can refine the grain size to about 50 µm, which is beneficial to obtain the better fluidityFluidity and reduce the hot tearingHot Tearing of AlCu based alloys.

In a number of aluminiumAluminium (AlAl ) alloys to date, scandiumScandium (Sc) additions have revealed a significant and beneficial effect on strengthening, even when added in small quantities. However, the strengthening response of the ternary AlAl -Si-Sc alloyAlloy system has been hampered by an apparent unfavourable interaction between siliconSilicon (Si) and Sc; forming the deleterious V-phase (AlSc2Si2) and thus limiting the allowable Si-content to ~0.15 wt.%. In this study, phase diagramsPhase diagrams were calculated using CALPHADCalphad and utilised to design AlAl -Si-Sc alloy compositionsAlloy compositions and heat treatment parameters. The AlAl -Si-Sc alloys were processed using a conventional route of wrought aluminiumWrought aluminium semi-products. A hardnessHardness improvement of up to 30% was achieved for the alloys containing Si as high as 0.8 wt.% in the F-temper. The improved hardnessHardness was mainly attributed to the homogeneously distributed, coherent, (AlAl ,Si)3Sc nano-dispersoidsNano-dispersoids in the α-AlAl matrix formed during a low temperature annealing treatment and retained in the F-temper condition.

The use of scandiumScandium in aluminum alloysAluminum alloys is of interest due to the strengthening effects, particularly at elevated temperatures. This work describes two different approaches to the use of scandiumScandium that have not been well studied. The first is the combined use of scandiumScandium and ceramic particles to improve the elevated temperatureElevated temperature performancePerformance of aluminum alloysAluminum alloys . The second is preliminary work in using scandiumScandium in combination with ceriumCerium , another element that has demonstrated good high temperature performancePerformance .

Light-weighting of vehicles drives the development of Aluminium alloys with improved strength and formability. An opportunity to achieve this goal is using Scandium (Sc). The beneficial effects from Sc comes from the formation of nano-sized Al3Sc dispersoids. Detrimental interactions between Sc and Silicon (Si) has limited the uptake of Sc in 6xxx alloys. The first step towards developing Sc containing 6xxx-series is to understand the as-cast microstructure and the effect of subsequent heat treatment on the dispersoids. This work uses isochronal ageing trials on a series of Al-Mg-Si-(Sc)-(Zr) model alloys. The evolution of hardness and conductivity is recorded to indirectly characterize the precipitate sequence. Transmission electron microscopy is used to further characterize the morphology and kinetics of MgSi precipitates and Sc/Zr dispersoids. The precipitation of Sc was altered by the presence of Si, and hence it is concluded that a non-traditional homogenization treatment is required for these alloys.

Scandium has a known beneficial effect on the strength of aluminium alloys. In particular, the strength of weld metal in a 5 series alloy can be significantly increased by scandium additions to either the weld filler rod or the base metal plate. The emerging technology of wire arc additive manufacturing (WAAM) provides for fast welding deposition rates of 3D structures. Because the whole piece is weld metal, scandium additions to the weld wire would appear to offer an opportunity for increased strength of articles produced by WAAM processes. This paper examines various addition levels of scandium to AA5183 aluminium alloy. AA5183 welding wire is commonly used for welding of AA5083 plate, commonly used in marine and automotive applications. It was shown that significant levels of strength improvement were possible with scandium additions of 0.2–0.5%. Further additional strength improvement was made possible by a post-weld heat treatment.

Benefits of alloying Sc with aluminum resulting from the precipitation of coherent Al3Sc dispersoids, including refined microstructure, increased strength, and improved weldability, have been demonstrated for a number of commercial aluminum alloys. Historically interactions between Sc and Si have limited the benefits of Sc additions in Al-Mg-Si 6xxx alloys. The first step towards developing a Sc containing 6xxx-alloys requires studying the interaction between Si and Sc. Hence, this work characterizes the aging response associated with precipitation of Si-modified Al3Sc dispersoids in a Sc-containing Al-Si alloys. The work reported in this paper focuses on understanding the breakdown of the solid solution of Sc in Si-containing aluminum alloys. Results of this study can be used to define heat treatment schedules for scandium containing 6xxx alloys.

Small additions (0.05–0.1 at.%) of scandium to 5000 aluminum alloys (3–5 at.% Mg) can strengthen these alloys to make them competitive with high strength aluminum grades (e.g. 2000, 7000). A common issue with 5000 series aluminum alloys, however, is the formation of Lüders bands, strain heterogeneities caused by high concentration of Mg in solution. Scandium additions in aluminum alloys form Al3Sc nano-dispersoids which can homogenize strain throughout the material, while zirconium additions stabilize the dispersoids to prevent coarsening. This study develops processing methods and compositions to optimize strength and formability in these wrought alloys. Coherent, semi-coherent, and incoherent precipitates were produced to study the effect of dispersoid size and to assess the tradeoff between production requirements and mechanical properties. Heat treatments were developed to attain these specific structures.

LCA approach guidelines for automotive sector recently introduced [1, 2] highlighted how much important is working on decarbonisation of AlAl castingCasting processes to produce vehicle components. Broadening use of secondary aluminumSecondary aluminum alloys, instead of high energyEnergy intensive primary aluminum alloysAluminum alloys , is key for environmentEnvironment preservation. Unfortunately, primary aluminum alloysAluminum alloys are preferred by automotive OEMs because impurities (mainly Fe) present in secondary aluminumSecondary aluminum alloys can cause mechanical performancePerformance decrease. Semisolid-state process route is still thought to drastically reduce some physiologic castingCasting defects, thus positively balancing decrease by impurities. Basing on these premises, a pre-industrial prototype 4-columns 700 kN clamping force vertical castingCasting machine has been designed and constructed to cast secondary aluminumSecondary aluminum in two modes: medium-pressure die castingDie casting and semisolid state. Investigation on A356 secondary alloys samples obtained by both process routes have been investigated in order to compare microstructureMicrostructure integrity and key-features impacting on final mechanical properties.

Al3Ti particulates (5 vol%) were produced in situ via aluminum-K2TiF6 reactions in an Al-7Si alloy. The effects of strontium (Sr) addition (200 ppm) on the microstructure and mechanical properties were studied. In addition to the modification on the morphology of eutectic Si, Sr addition resulted in the reduction of Al3Ti particulate sizes. As a result, the yield strength, tensile strength and ductility of composites with Sr addition are simultaneous improved compared to composites without Sr addition for both as-cast and T6 states. The enhanced mechanical properties are attributed to the small-sized Al3Ti particulates and a refined microstructure.

In automotive cable harness production the substitution of copperCopper by aluminumAluminum wires is pursued more and more as the weight of aluminumAluminum is 50% lower than that of copperCopper considering to reach the same conductivity and an additional cost decrease of 2.5 times. Moreover joining aluminumAluminum wires to copperCopper terminals is often realized via crimping, which shows several disadvantages especially for cross sections of more than 10 mm2, e.g. reduced conductivity due to the oxide layers on aluminumAluminum or electrochemical corrosionElectrochemical corrosion of the contact points. Ultrasonic metal welding is a promising technologyTechnology , which can avoid these problems. With the availability of torsional ultrasonic weldingUltrasonic welding machines, joining of aluminumAluminum wires with cross sections of up to 200 mm2 is possible. Recent investigations focus on the microstructural and mechanical properties of large cross section aluminumAluminum wire to copperCopper terminal joints whereas current joint strengths reach values of 31% of the weaker base material.

The effect of quench rate and aging treatment on strain distribution within the grains and across the grain boundaries has been quantified in Al-Mg-Si-Mn-Fe extrusion alloys using high resolution digital image correlation. The results show that cooling rate significantly influences the degree of strain localization at the grain boundaries and eventually fracture strain of the alloy.

AluminumAluminum extrusions are being increasingly utilized as structural components in automotive applications. The objective of this work is to evaluate the effect of through thickness crystallographic textureTexture gradients on material mechanical behaviour. This has been studied using a combination of experiments (i.e. pilot scale extrusions and stress-strain curves with the R-value to characterize plastic anisotropyAnisotropy for different loading directions) and the visco-plastic self-consistent (VPSC) polycrystal plasticityPolycrystal plasticity simulations on a modelModel alloyAlloy system. Two limiting conditions were examined, i.e. unrecrystallized and fully recrystallized conditions. The results of electron backscatter diffraction (EBSD) characterization show that there is a significant through thickness variation in texture for both cases. However, the implications of the texture gradient on the macroscopic plastic response were relatively minor for the unrecrystallized case but quite significant for the recrystallized case. This was manifested as a strong difference in the contraction of the surface layer compared to the centre of the extrudate, particularly in the case of tests at 45° and 90° to the extrusion direction. This was rationalized in terms of the differences in texture between the surface and the centre using VPSC simulations. Finally, it was proposed that this effect be explored in future work as it may have important implications on the surface stress state which could affect damage initiation, growth and coalescence, particularly in bending situations.

Industrial scale nanostructuring via High ShearHigh shear Deformation (HSD) can alter the properties of metals and alloys to increase their performancePerformance and extend their lifetimes. These factors in combination facilitate the use of lightweight alloys for transportation applications. This work examines how nanostructuring aluminum alloysAluminum alloys can improve the fuel economy of vehicles by reducing the weight of electrical wires. Applying HSD non-isothermally alters precipitationPrecipitation , increasing the electrical conductivityElectrical conductivity of AlAl -Mg-Si alloys to 57% IACS while also increasing strengthStrength by over 50%. Microstructural analysisMicrostructural Analysis of AlAl alloys before and after HSD processingProcessing was performed to show how HSD changes grain size and precipitate size distribution.

The automotive industry has long been interested in Al alloyAl alloy sheet material for body construction to reduce weight. Nevertheless, it is important to get a deeper understanding of the formabilityFormability of AlAl alloys to further this applicationApplication . Previous studies have illustrated that the initial textureTexture and its evolution during forming can significantly affect the formabilityFormability . Here, the effect of textureTexture gradients, within commercially processed AA6xxx series alloys sheets, on predicted forming limit curves (FLCs)Forming limit Curves (FLCs) is examined. ExperimentalExperimental measurementsMeasurements at the surface, 1/6th, 1/3rd and mid-plane reveal that all the materials examined possess recrystallization textures, with Sample #4 having the weakest and Sample #2 the strongest intensity. Sample #2 also exhibited the strongest textureTexture gradient where the surface is comprised of strong cube textureTexture while the interior also possesses a fibre textureTexture with Goss component. The experimentalExperimental textures were used as inputs to a Marciniak–KuczynskiMarciniak-Kuczynski (M–K) based viscoplastic self-consistent (VPSC) polycrystal plasticityPolycrystal plasticity code for FLC prediction. The absolute level of formabilityFormability was observed to vary within the samples. Discrepancies on the stretching side are due to the deviation from proportional loading in the Nakajima test, which is not accounted for in the modelModel . Simulations carried out using textures from specific sections confirm a previously observed phenomenon that the cube textureTexture enhances the formabilityFormability on the stretching side whereas the Goss component degrades it.

Acoustic streamingAcoustic streaming is a key factor in ultrasonic castingCasting of aluminum alloysAluminum alloys because it determines heat and mass transfer, and thus affects the temperature distributionTemperature distribution , solidificationSolidification phenomena, solute transport and crystal growth. However, measurement and prediction of acoustic streamingAcoustic streaming in molten aluminumAluminum present a big challenge due to high temperatures and acoustic streamingAcoustic streaming complexity. In this work, a numerical modelNumerical Model has been developed to simulate acoustic streamingAcoustic streaming in molten aluminumAluminum . The modelModel allows predicting generation of cavitationCavitation bubbles, sound wave propagationPropagation and attenuation due to interaction with the bubbles, and fluid flow. The model validationModel Validation has been performed by comparing the predicted and measured acoustic streamingAcoustic streaming in waterWater model . Good agreement between these results suggests that the modelModel can be used to predict acoustic streamingAcoustic streaming in actual castingCasting processes. However, a number of issues still remain to be solved particularly an accurate simulation of bubble oscillations.

The quantification of acoustic pressures in liquid metals is of paramount interest for the optimizationOptimization of ultrasonic melt treatment (UST) of large volumes. Until recently, the measurementsMeasurements of acoustic pressureAcoustic pressure and cavitation intensityCavitation intensity in a melt were cumbersome and unreliable due to the high temperatures and the lack of suitable instruments. These difficulties imposed strict limitations on the experimentalExperimental and numerical investigation of cavitation and bubble dynamics within liquid metals. In recent years, our group used a unique calibrated high temperature cavitometer to measure cavitation activity and acoustic pressures in liquid aluminum. Phenomena such as acoustic attenuation, shielding, and cavitation intensityCavitation intensity have been studied. These measurementsMeasurements were also used to validate a non-linear acoustic numerical model applicable to flow in bubbly liquids subject to acoustic cavitationAcoustic cavitation . Both experimentalExperimental and numerical characterizationCharacterization of the acoustic and flow fields provides a powerful tool to optimize cavitation processingProcessing in liquid metals.

In this paper, we present some highlighted findings from our recent research on real-time and in situ studiesReal-time and in situ studies of the fundamentals of ultrasonic melt processingUltrasonic melt processing , including (1) ultrasonic bubble implosion, oscillation in liquid and semi-liquid (semi-solid) metals and their interactions with the growing solidifying phases; (2) enhanced acoustic metal flow and their impact on the liquid-solid metal interface. The real time experimentalExperimental phenomena were interpreted with the aid of calculating the propagationPropagation of acoustic pressureAcoustic pressure in liquid metals using the Helmholtz equation and bubble wall pressure and velocity profile during bubble oscillation using the classical Gilmore modelModel . The research provides unambiguous real-time evidence and robust theoretical interpretation in elucidating the dominant mechanisms of microstructureMicrostructure fragmentation and refinement in solidificationSolidification under ultrasoundUltrasound .

To study the microstructureMicrostructure formation including columnar equiaxed transformation in the presence of ultrasoundUltrasound , a set of new equipment consisting of a 2-zone furnaceFurnace and an ultrasoundUltrasound system was set up in the Ultrasonic and SolidificationSolidification ProcessingProcessing LaboratoryLaboratory at the University of Alabama. The 2-zone furnaceFurnace is an induction furnaceFurnace with two separate coils (a top coil and a bottom coil). By controlling both the top and bottom coil output power independently, the furnaceFurnace can create various temperature gradients including a mushy zoneMushy zone and cooling rates in different regions of the graphite crucible. A water-cooled chill block was applied at the bottom of the crucible. The ultrasoundUltrasound probe was inserted at the top of the crucible. A numerical modelNumerical Model was developed to predict the temperature gradients and mushy zoneMushy zone evolution in the crucible. The influence area of the ultrasoundUltrasound on the A356 microstructureMicrostructure was studied.

Contactless ultrasoundContactless Ultrasound uses Lorentz forces from a secondary coil to induce ultrasonic vibrations in alloy meltsAlloy Melts . To achieve pressures high enough for cavitationCavitation , resonanceResonance is required. However, the prediction of the resonant modes for a melt in a crucible is complex, due to the transmission and reflection of sound within the crucible walls. Two acoustic models, one solving a simplified momentum equationMomentum Equation in the time domain, the other solving the Helmholtz equation in the frequencyFrequency domain are compared. The frequencyFrequency domain modelModel allows a fast sweep of frequencies for resonanceResonance tuning, and the transient modelModel enables a more detailed analysis. ValidationValidation is against analytic test cases derived with boundary conditionsBoundary Conditions specific for the liquid metal medium and against experimentalExperimental data obtained in an aluminumAluminum meltingMelting crucible. Results confirm that sound transmission into the crucible walls has a significant effect on resonant frequencies and needs to be accounted for.

Understanding the interaction of nano/micro-particles with evolving microstructures during solidification is critical for developing new materials with improved mechanical properties through either particulate reinforcement and/or via microstructural refinement. In this study, we investigate the influence of nanoparticles on the evolving dendrites in both Mg and Al based metal matrix composites via in situ synchrotron tomography. Ultrasonic treatment was applied during the raw material preparation to break the particle agglomeration. The solidification of primary dendrites was characterized and quantified. The results reveal the underlying physical mechanisms that enable nanoparticles to modify the grain size in both alloy systems. These insights into dendrite evolution help both to inform and validate numerical models of the solidification microstructures of metal matrix composites.

Recent experiments using electromagnetic levitation in reduced gravity have confirmed prior observations of anomalous nucleation of the solid in undercooled melts under specific conditions. All indications are that this effect is dynamical, not chemical: the same sample undercools over 300 °C before and after the anomalous event, but maintains the liquid state for only a few seconds when held at a more modest undercooling in the range of 0–50 °C. The new experimental results and related modeling will be examined in comparison to the hypothesis that the solidification is triggered by cavitation in the melt. This platform may provide data relevant to a better quantitative understanding of the effect of ultrasonic processing on grain refinement of terrestrial castings.

The application of ultrasound to casting process can improve the quality of the casting through the effects of grain refinement, degassing, wetting, deagglomeration and dispersion. For treating large volume of liquid metal, Computational Fluid Dynamics (CFD) study has recently developed an analysis tool capable to model acoustic streaming and cavitation in liquid metal. In general, the cavitation zone is a very small region in fluid, acoustic streaming is main factor for scale-up of ultrasound process because that is a non-linear physical effect which can assist in effective dispersion of cavitation bubble with propagation of the ultrasonic wave in liquid. But previous studies of CFD have limited theoretical model revision to accurately predict cavitation phenomenon. Therefore, this study is focused on the effect of ultrasonic injection conditions and fluid characteristics on acoustic streaming. The acoustic streaming velocity in fluid was measured using Particle Image Velocimetry (PIV) and CFD modeling was performed to predict the acoustic streaming and treatment time in specific volume of fluid by ultrasonic injection.

Ultrasonic treatmentUltrasonic treatment (UST) during the solidificationSolidification of commercial purity Mg was investigated over different time-temperature ranges: (i) UST in the liquid region only (ii) during the transition from liquid to solid including the onset of nucleationNucleation and (iii) UST initiated before the end of solidificationSolidification but well after the onset of nucleationNucleation of α-Mg for the formation of equiaxed grainsEquiaxed grains . If UST is terminated at the end of the liquid stage or above 650 °C there is a negligible effect on the final grain size. The solidificationSolidification treatment (case ii) produces incremental grain refinementGrain refinement when UST is applied from 690 to 650 °C for 1 or 2 min, however, from 750 to 650 °C for 3 or 4 min shows only coarse, non-equiaxed grainsEquiaxed grains . Introducing UST well after the onset of solidificationSolidification produces a region with the finest grains of all treatment ranges investigated. The degree of grain refinementGrain refinement was found to be temperature dependent where low temperature initiation resulted in a higher number density of grains. The mechanismMechanism of grain formation during UST is discussed with respect to the processingProcessing parameters and thermal conditions driving the formation of equiaxed grainsEquiaxed grains .

Solidification microstructures formed under high-intensity ultrasonication are systematically investigated in various Al and Mg-alloys. The range of microstructures examined include primary grain structure, intermetallic compounds (IMCs), regular and irregular eutectics. Extensive grain refinement is observed in all alloys, especially in the areas of cavitation, further facilitated by the presence of solute. Heat treatability of the ultrasonicated alloys is enhanced as the fine-grained microstructure reduced diffusion distance. Regular lamellar eutectic microstructure is observed to degenerate under cavitation. Irregular eutectic and IMCs are modified from coarse plates or complex morphology into compact polygonal shape. Result suggests that ultrasonication increases nucleating particles and potency of nucleants. The modification of eutectic and IMCs predominantly occurs through coarsening and spheroidisation in the area of intense cavitation. While grain refinement effect is noticed in the entire ingots assisted by acoustic streaming, eutectic modification effect dissipates rapidly outside the area of cavitation.

This work presents design and performance characteristics of large-size ceramic and metal sonotrodes for ultrasonic treatment of molten aluminum alloys in industrial and pilot scale casters. ANSYS software was used to predict vibration characteristics and to design sonotrodes of various shapes made of silicon nitride base ceramics or Nb-based refractory metals. The design concept is based on requirements that users actually need to apply the sonotrodes on industrial scale, particularly high vibration amplitudes and large diameters of working tip. Both these parameters were found to be determined by the sonotrode shape, connection reliability and material properties. A number of sonotrodes was fabricated and examined for their ability to treat aluminum melt in DC casting process in order to refine the solidification structure. Although the ability to refine the metal structure was about the same for sonotrodes of both types, the ceramics barbell sonotrodes demonstrated much better performance with respect to acoustical and chemical stability, especially at high temperatures. On the other hand, the metal sonotrodes were highly susceptible to cavitation erosion.

In this work, we have introduced power ultrasoundUltrasound in the sump during hot-top DC castingDC casting of 152 mm Ø billets to influence the aluminiumAluminium grain growth morphologyMorphology . Grains in the central part of the billetBillet are highly dendritic and elongated towards the sonotrode position in the sump. We suggest that ultrasoundUltrasound generates acoustic flow in the sump counteracting natural convectionConvection , thereby affecting the direction of grain growth; this is supported by numerical modellingNumerical Modelling . We found that macrosegregationMacrosegregation can be decreased by tuning the position of the sonotrode in the sump and the ultrasonic power. Apart from the central part of the billetBillet , the grain size was found to be significantly refined compared with the reference cast. This could be an effect of forced dendritic fragmentation by ultrasonic melt processingUltrasonic melt processing .

The cavitationCavitation bubble is essential for the ultrasonic degassingDegassing , however, the bubble could not be developed at the whole melt because of the threshold intensity for the bubble generation. The intensity of the ultrasoundUltrasound decreases exponentially with the propagationPropagation distance. The melt should be transferred to the effective volume that has the sufficient ultrasonic intensity to exceed the threshold for the cavitationCavitation generation. The important parameter to make melt transfer is the acoustic streamingAcoustic streaming induced by the ultrasoundUltrasound . This study is focused on the melt flow and the effect on the degassingDegassing level with the ultrasonic frequencyFrequency to improve efficiency of ultrasonic degassingDegassing . The increase of the ultrasonic frequencyFrequency and amplitudeAmplitude made the cavitationCavitation bubble density and the velocity of the melt flow increase, respectively. As the result, the degassingDegassing velocity could increase dramatically.

Ultrasonic vibration characterised by high-intensity and low-amplitudeAmplitude is one of the physical (or mechanical) means that can effectively refine the as-cast grain structure without using inoculant particles [1–8]. Computational models that quantitatively describe hydrodynamic fields induced by ultrasonics and the resultant microstructure evolution are an invaluable way to understand and optimise ultrasonic treatmentUltrasonic treatment (UST) processes, and the development of these models is crucial in taking advantage of UST as part of a casting process [9–12]. The current work investigates the effect of acoustic streamingAcoustic streaming on the evolution of microstructure of an Al-2Cu alloy during the application of UST numerically. A computation model based on CAFE (Cellular AutomationAutomation Finite Element) coupling fluid flow, heat transferHeat transfer , nucleationNucleation and grain growth was developed and validated by comparing the results of numerical simulations against physical experiments.

An ultrasound-based method for the detection of non-metallic inclusions in cast and wrought aluminum melts is being developed. Main objective of the development is to meet the requirements for a sufficiently fast and precise assessment of the present contamination grade in the melt with a handy and comparatively cheap set-up. First trials, using the Liquid Metal Cleanliness Analyzer (LiMCA) and Porous Disk Filtration Analyzer (PoDFA) method for comparison to evaluate the developed system, showed a very good correlation between the ultrasound results and the reference procedures. Defined types of inclusion particles with specific size ranges were introduced into a base aluminum melt with a purity of 99.8%. The settling curves were monitored by LiMCA and the ultrasonic detector. Furthermore, PoDFA samples were taken at certain points in the process. The trials prove the achievement of a detection limit down to a particle size of 20 µm and a particle concentration of less than 1000 particles per kg aluminum melt.

The acicular β-AlSiFe phase is most common but detrimental iron-containing intermetallic compounds (IMCs) in Al-Si casting alloys. In this study, ultrasonic field (USF) was applied to modify the acicular iron phases in Al-12Si-2Fe alloy. The results showed that USF treatment leads to different influence at different application temperature region. The application of USF at 720 °C facilitates the formation of blocky-shaped α-Al12Si2Fe3 phase and suppresses its conversion into the acicular β-Al9Si2Fe2 phase by the quasi-peritectic reaction. The amount of α-Al12Si2Fe3 increases with increasing applied time of USF. The ultrasonic cavitation-induced nucleation is responsible for the morphological modification and phase transformation. USF applied at 610 °C causes a fragmentation of β-Al9Si2Fe2 without composition change, and the cavitation-induced fragmentation is considered as the major reason.

The paper present a study on alloys of the Al-Mg system (5–6 wt%) strengthened with nonmetallic nano- and microparticles such as nanodiamond, TiB2 and their combination. The introduction of nonmetallic particles into the Al-Mg melt was carried out using master-alloys, a mechanical mixer and simultaneous ultrasonic treatment of the melt. In addition, when casting into the chill mold, the melt was subjected to vibration treatment before solidification. The castings obtained were transformed into sheets with a thickness of up to 10 mm by hot rolling. The structure of the alloys obtained in the cast state and after deformation treatment of both initial (without particles) and containing nanoparticles was studied using metallography methods, i.e. optical and scanning electron microscopy. Analysis of the mechanical properties of the alloys under loading was carried out. Vickers microhardness and Brinell hardness were also studied.