Light Metals 2022

The GreenGreen AluminiumAluminium phenomena although recent in notion, has been materializing over the last century with the first dedicated hydroelectric power stations for aluminiumAluminium production being commissioned early in the twentieth century. With the EU emission target strategy in full swing, individual producers setting their own values and speculation on the formation of a newly indexed metal, producers, technology suppliers, and regulators are trying to common ground to materialize a niche portion of aluminiumAluminium production to meet the emission-related targets. The carbon dioxide makeup of aluminiumAluminium production is dominated by the electrolytic reaction followed by the anode consumption and then the Bayer process. The industry has spent significant efforts in decarbonizing the former two, the latter still needing strong conceptual development. This paper intends to explain the conceptual contribution towards GreenGreen AluminiumAluminium from the perspective of a Bayer process technology supplier.

The shrinking core modelShrinking core modelShrinking core model is used in many applications, including simulationsMathematical simulation on alumina and limestone calcinationAlumina calcination. It helps to predict product properties, i.e. phase composition, reactivity, and strength. Its application is limited by computational costs and the complexity of known numerical solutions of transfer equations for mass, heat, concentration, and moment in the core and shell of a particle with moving reaction front, where the material properties are broken. The paper proposes to integrate the shrinking core modelShrinking core model equations using a deep learningDeep learning neural network which allows obtaining a high-quality solution much faster as compared with finite difference methods. The paper discusses the examples demonstrating the use of a new fast solver in the model of alumina flash calciner to calculate LOI for each particle size grade. The paper demonstrates the similar way to solve the problem of burning limestone in a shaft kiln.

The Metso Outotec Calciner OptimizerCalciner optimizer is a digital solution to actively control and optimize alumina calcination plants. It is today in continuous, close to 100% availability, operation at Companhia Brasileira de Alumínio (CBA). The paper covers the architecture of the digital solution, the impact on CBA calciner operation, and how detailed process understanding is integrated in a digital form into the daily process operation. The close cooperation between CBA process experts and Metso Outotec digital and process experts forms the basis of a successful implementation. Results are shown and discussed in this paper, proving significant energy savingsEnergy savings when operating the plant with the Optimizer. Using the Optimizer provided a reduction in specific fuel gas consumption and greenhouse gas emissions. Further, the fluid bed calcination process know-how, combined with the advanced digital Optimizer solution, represents an enabler for future operational improvements.

Alumochloride technologyAlumochloride technology can be used to obtain high value-added products from natural or industrial raw materials. Such products include, for example, pseudoboehmitePseudoboehmite used for refining catalystsCatalyst. Pilot samples have been successfully tested for distillate hydrotreating to produce Euro-5 compliant diesel fuel (<10 ppm residual sulfur). One more product is polyaluminum chloridePolyaluminum chloride that is used as a coagulantCoagulant for potable water conditioning and effluent treatment. The said process complies with international standards and allows varying Cl/Al ratio within the range of 1.2–2.4 thus enabling to select the coagulantCoagulant for different water types. Moreover, the process of High purity aluminaproduction high purity aluminaAlumina (5 N) has been developed. This product is used to grow sapphires (for LED, smartphone screens) and to cover separators for Li-ion batteries to improve their thermal stability and power intensity. The proposed processes can be established as individual production set-ups or integrated into aluminaAlumina production by the alumochloride technologyAlumochloride technology.

Physicochemical property of sodium aluminate solutionSodium aluminate solution is an important theoretical basis for caustic process for alumina production, referring to digestion, hydrolyzation, settling, precipitation, and evaporation processes operation, which directly affect energy consumption and alumina quality. Thus, it is necessary to explore one method to conduct physical propertyPhysical property prediction for liquor. Based on the Bayer process, the effects of relative factors on the physical propertiesPhysical property of liquor were investigated, besides orthogonal testOrthogonal test was designed to analyze the influence sequence of various factors like molar ratio of sodium aluminate, sodium carbon content, silicon index, and alumina content in the liquor, which can provide us with guidance for establishing appropriate mathematical models to calculate the physicochemical property of sodium aluminate solutionSodium aluminate solution based on electric conductivityElectric conductivity analysis during alumina production process, and the results show that the order of each factor from primary to secondary is alumina content, caustic content, sodium carbon content, and silicon index, which can bring us instructive guidance when establishing appropriate mathematical models to predict the physicochemical property of sodium aluminate solutionSodium aluminate solution based on electric conductivityElectric conductivity during alumina production process.

High-iron red mudHigh-iron red mud is an alkaline solid waste generated during the process of alumina production by Bayer process. At present, the annual emissions of high-iron red mudHigh-iron red mud are about 50 million tons in China. Due to strong alkalinity, the comprehensive utilization of high-iron red mudHigh-iron red mud is limited. In order to realize high-value utilization of such material, a new smelting reductionSmelting reduction technology followed by production of cement clinker from reduced slag was proposed. This paper focused on the smelting reductionSmelting reduction of high-iron red mudHigh-iron red mud. The effects of temperature, mole ratio of C/O, additive ratio of CaF2, and basicity on recovery rates of iron and sodium were investigated in detail. The results showed that the recovery rates of iron and sodium were 98.36% and 38.45%, respectively. The chemical compositions of pig ironPig iron meet the national standard of pig ironPig iron for steel-making.

Aluminum drossAluminum dross is a hazardous solid waste produced in the process of electrolytic aluminum or cast aluminum production, with annual emission of more than 3 million tons. Fluoride, aluminum nitride, and soluble salts contained in aluminum drossAluminum dross lead to environmental pollution and health hazard. In this paper, a method of harmless treatmentHarmless treatment of secondary aluminum drossAluminum dross was proposed. The effects of temperature, liquid–solid ratio, time, and stirring speed on removal rateRemoval rate of nitrogen, fluorine, and chlorine were investigated in detail. The results showed that the removal ratesRemoval rate of each element reached the maximum at temperature of 80 °C, liquid–solid ratio of 3:1, time of 2 h, and stirring speed of 400 r/min. The removal ratesRemoval rate of nitrogen and fluorine were 62.8% and 77.6%, respectively, and the chlorine was completely removed. The research provides possibility for the harmless treatmentHarmless treatment and resource utilization of secondary aluminum drossAluminum dross.

Red mud and waste cathode carbon block are two major solid wastes of the aluminum industry. In this study, an innovative method has been proposed for co-treatment of red mud and spent cathode carbon blockSpent cathode carbon block to reuse carbon and recover iron by melting reductionMelting reduction. The effects of parameters such as temperature, alkalinity, reaction time, and the CaF2 addition on the process were investigated. According to the experiment, the suitable reaction conditions were the reduction temperature of 1350 ℃, the alkalinity of 1.0, the reaction time of 30 min, and the optimal CaF2 addition was 10 g. The Fe recovery rate was 91.60% which can be directly used for electric furnace steelmaking. This work should help to improve the future large-scale, high-value, and zero waste utilization of red mud. It was also of great significance for the harmless treatment of spent cathode carbon blocksSpent cathode carbon block and alleviating the shortage of iron ore resources in China.

With the advantages of large reserves and easy access, low-grade bauxiteLow-grade bauxite was an important proportion of aluminum resources. However, low-grade bauxiteLow-grade bauxite was difficult to meet the grade requirements of the Bayer process, and it was necessary for low-grade bauxiteLow-grade bauxite to be pre-desiliconized. In this paper, a typical low-grade bauxiteLow-grade bauxite in China was taken as the research object, and the thermal activationThermal activation performance and pre-desiliconizationPre-desiliconization behavior of low-grade bauxiteLow-grade bauxite were studied. The thermal activationThermal activation results showed that the phase component of bauxite had a significant variation at 700 °C. The X-ray diffraction peaks of kaolinite almost disappeared, while diaspore was transformed into synthetic corundum. In the pre-desiliconizationPre-desiliconization process, the silicon component had the highest extraction rate at the beginning 45 min of leaching, while the alumina component was relatively inert. Finally, the mass ratio of alumina to silica of low-grade bauxiteLow-grade bauxite was increased from 2.3 to 6.5, which meets the requirements of the Bayer process.

In recent years, automotive demands for greater fuel efficiency, lower fuel consumption has driven advanced lightweight aluminumAluminum high-pressure vacuum casting applications for the body-in-white structure. Cosma, the body and chassis group of Magna International, initiated a research program dedicated to developing an optimized low-cost aluminum alloy for structural high-pressure vacuum die-cast automotive components. The mechanical properties are one of the most important requirements for high-pressure vacuum die castingsHigh pressure vacuum die castings. Ductile properties are specified to ensure crash behavior and to allow for the use of self-piercing rivets during joining to the body assembly. This aluminumAluminum alloy development program comprised both theoretical and experimental elements to arrive at a self-hardening Aural 5M (M is for modified) alloying system that satisfies the desired mechanical properties in the as-cast (F temper) and after the part is subjected to an artificial age during the Original Equipment Manufacturers paint shop cure oven exposure. In addition, for manufacturability of the next-generation ultra-large body castings, new aluminumAluminum alloys are also required to exhibit enhanced castability. This paper discusses the improved properties and manufacturability of Magna’s new Aural 5M aluminumAluminum alloy.

An Al11.3Ce3.2Ni1.2Mn (wt%) alloy was cast in a wedge mold configuration, sectioned, and tested at room temperature and 250 °C to assess the alloy’s high-temperature performance. The wedge mold configuration provided a range of cooling rates from 0.18 to 8.42 °C/s. Optical microscopy, scanning electron microscopy, and energy x-ray dispersion were used to verify cooling rates, phase size and morphology, and phase composition, respectively. The most common phases were primary and eutectic Al11Ce3 and Al23Ce4Ni6. Both the primary phases presented in blocky morphologies and the eutectic phase had a thin lath structure. Room temperature UTS ranged from 107 to 131 MPa, and the 250 °C UTS ranged from 91 to 108 MPa. UTS retention was observed in the range of 75–83% at 250 °C. It was also found that comparing the room temperature and 250 °C tensile tests results, the Al11.3Ce3.2Ni1.2Mn alloy exhibited a 14–61% greater modulus of elasticity at 250 °C.

The effects of Ti addition on the microstructural evolution and mechanical properties of Al–7.6Zn–2.6Mg–2.0Cu–0.1Zr alloy were investigated at each process step such as casting, extrusionExtrusion, solution treatment, and aging. The addition of titanium causes refinement of both the grains and bulky η-Mg(Zn,Cu,Al)2 particles in the as-cast alloys. After hot extrusionExtrusion, the Ti-added alloy has increased amounts of recrystallized grains by particle-stimulated nucleation, decreasing the strength of the as-extruded alloy. Titanium additionTitanium addition causes size decrease of L12 precipitatesPrecipitate and increases the number density of them while substituting Zr site with Ti, that is, Al3(Zr,Ti). Besides, the Al18Mg3Ti2 phase is formed by Ti addition during solution treatment, which acts as a heterogeneous nucleation of η precipitatePrecipitate. The strength of the aged alloys is improved by the formation of fine L12 precipitatesPrecipitate, grain refinement, and the refinement of bulky η-phases.

The paper investigates the effect of tungstenTungsten nanoparticlesNanosized particles on the structureStructure and mechanicalMechanical properties of aluminumAluminum 5056 alloy. Using optical and scanning electron microscopy, the structureStructure of the AA5056-W composite and the initial alloy is investigated. Introduction of 0.5 wt. % of tungstenTungsten nanoparticles does not modify the structureStructure of the aluminumAluminum alloy, but due to dispersed hardening, it can increase the hardness and the values of the yield stress, ultimate tensile strength, and maximum deformations before fracture of the metal matrix. The Orowan mechanism prevails in increasing the machinical properties of aluminumAluminum 5056 alloy with dispersed hardening with tungstenTungsten nanoparticlesNanosized particles. The destruction of materials is caused by the uneven distribution of tungstenTungsten nanoparticlesNanosized particles in the aluminumAluminum matrix.

Novel applications of lightweight alloys in various fields (e.g., automotive and aerospace) demand even enhanced material characteristics like improved mechanical propertiesMechanical properties and higher resistance against corrosion. Apart from modifying the alloy’s composition within specified limits, micro-alloying is a valuable tool to aim for improved mechanical propertiesMechanical properties and/or corrosion resistance. This study puts shed light on how this affects mechanical propertiesMechanical properties and corrosion behavior. Three different alloying compositions of EN AW-6056EN AW-6056 (standard, high alloying element concentration and, 0.025 wt.% Sn addition) were tested. The influence of composition on micro-structure, mechanical propertiesMechanical properties and corrosion resistance was then evaluated.

The Al–Si alloying system is widely used for the most common aluminum casting alloys. However, there is strong demand for new types of casting alloys that can face increased requirements to the material performance especially in an as-casted condition. The Al–Ca alloying system has good perspectives due to the possibility of obtaining dispersed eutectic (Al) + Al4Ca in the cast state without modification and heat treatment. The investigation of Al–Ca alloys with different Ca content, as well as the influence of various alloying elements, such as Zn, Si, Fe, and Mg, is necessary for the development of industrial alloy compositions. The authors investigated the effect of the content of Ca and other alloying elements on the structure, technological, and strength properties of the Al–Ca alloy during high-pressure casting. It also shows the possibility of increasing the strength properties of the alloy due to the formation of ternary eutectics in the alloy.

For investigating the effect of bismuth addition on microstructureMicrostructure change in AlMgSi aluminumAluminum alloys, a standard 6082 aluminum alloy is selected due to its usage, especially in the railway industry. A direct chill casting method was used to produce 14-inch billetsBillet casting in ASAŞ Aluminum’s prototype casting facility. After billet production, homogenization heat treatment was applied at 540 °C for 6 h to minimize the segregation and stabilize the precipitate distribution. Samples were taken from the billetsBillet casting both before and after the homogenization process. A microstructural investigation was conducted with optical microscope and SEM to understand the change between the Bi-added 6082 and the standard alloy. In addition, cast billetsBillet casting were preheated and extruded at 530 °C at 62 MN press. Following the extrusionExtrusion, water spray quenching is applied. For the artificial aging, 185 °C is applied for 5.5 h. Although research is still in progress, macroanalysis and fracture-type analysis have been completed and it is suggested that further research needs to be done in order to limit or eliminate the defects that have arisen due to Bi additionBi addition.

Nanoparticles have been used to facilitate processing and strengthen Al alloysAl alloys in solidification processing. However, the potential reactivity of Si and its compounds (e.g., β-Mg2Si) with TiC nanoparticles at high temperatures makes solidification processing challenging for Al–Mg–Si containing TiC nanoparticles. Given the broad applications of Al–Mg–Si alloys, how TiC nanoparticles affect its solidification processing and resultant properties is of significance. Here, we systematically studied the modified phase and composition by TiC nanoparticles in as-cast and heat-treated Al–Mg–Si alloys. The interaction between TiC- and Si-rich phases like β-Mg2Si has been analyzed. The mechanical performance including hardness and tensile properties, and fractography have been studied and correlated with the TiC-induced nano-treating effects. This study provides useful insights to develop high-performance Al–Mg–Si alloys with ceramic nanoparticles.

Iron is considered as the harmful impurity in recyclingRecycling of aluminium alloys. Presence of iron results in formation of brittle intermetallics compounds in these alloys. The size, shape, and distribution of brittle iron intermetallic particles significantly influence the mechanical properties of these alloys. In this study, chemical modification method such as the combined addition of Mn and Sr to the melt was used to modify the morphology of iron intermetallics in Al–Si alloysAl-Si alloys. Al-7Si with 0.6%Fe and Al-7Si with 2%Fe alloys were prepared by melting and casting. Subsequently these alloys were modified with the addition of Mn and Sr. SEM-FIB was used for 3D visualisation of iron intermetallic particles in modified alloys. Microstructural results show that the addition of Mn and Sr resulted in modifying the plate-like brittle intermetallics to flower/star-shaped intermetallic compounds. Tensile test results show that the increase in iron from 0.6 to 2% significantly decreased the tensile strength and elongation of the alloy. Modification of Al-7Si-2Fe with Mn and Sr improved the tensile strength and elongation compared to Al-7Si-0.6Fe and this improvement is due to morphological modification of intermetallic compounds with Mn and Sr.

Under rapid solidification conditions, Al-33wt%Cu eutecticAl-Cu eutectic droplets develop a microstructure composed of two different eutecticAl-Cu eutectic morphologies: an undulated eutecticAl-Cu eutectic, assumed to grow during recalescence, followed by a lamellar eutecticAl-Cu eutectic growing post recalescence. In situ heat treatments are applied to Al-33wt%Cu droplets rapidly solidified using impulse atomization to investigate the dynamic effect of temperature and time on the two eutecticAl-Cu eutectic morphologies. The samples are aged in situ in an SEM using a heating stage developed by Norcada. The undulated region coarsens faster than the regular eutecticAl-Cu eutectic, with fine lamellae still visible at 500 °C. At 525 °C, and both regions are indistinguishable from each other. At 550 °C, the droplet is fully liquid, but retains its spherical shape due to the oxide skin. This technique enables observation and quantification of in situ aging, coarseningCoarsening and solidification experiments.

A new family of cast Al–Fe-based eutectic alloy system with Zn and Mg as strengtheners through precipitation has been developed and validated for use in structural automotive applications. High-vacuum high-pressure die casting (HV-HPDC) was used in the casting of structural plates using the Nemalloy HE700 alloy. Typically, HPDC cast components exhibit anomalously large grains in the cast microstructure termed as pre-solidified grainsPre-Solidified Grains (PSG). These PSGPre-Solidified Grains did not present themselves as a critical defect until structural castings were manufactured with this process route. The PSGsPre-Solidified Grains in the as-cast microstructure shall be characterizedCharacterization through quantitative metallography and the effects of varying shot interval delays shall be presented.

The need for lightweight and high-strength advance materials in the form of metal-matrix composites with micron-sized particulate reinforcements has received considerable attention within automotive and aerospace industry. Ultrasonic melt treatment of Al alloys offers a sustainable and eco-friendly approach to produce structural refinement through enhanced heterogeneous nucleation obtained from combined effect of sono-fragmentationFragmentation of primary intermetallicIntermetallics/dendrites and de-agglomerationDe-agglomeration of non-metallic oxidesOxides/inclusions. However, owing to complexity of the process, understanding of the underlying mechanisms behind these effects is still rudimentary and lacks experimental evidences. In this paper, an insight into the underlying mechanism of fragmentation and de-agglomeration of Al3Zr intermetallicIntermetallics and MgO oxide particles, respectively, in water is presented. Real-time high-speed imaging was performed to discern the dynamic interaction of cavitation with free-floating particles in a controlled ultrasonic environment. In situ observations revealed that intermetallicIntermetallics breakage primarily occurs due to propagating shock waves, whereas the oxide de-agglomerationDe-agglomeration happens through microbubble cluster collapses close to the agglomerate.

Microstructure of nodular primary silicon crystal in hypereutectic Al–Si alloyAl–Si alloy has been metallo-graphically studied. Etched growth traces were used to investigate the growth mechanismGrowth mechanism of nodular silicon crystalNodular silicon crystal. Silicon nodule as an equiaxed polyhedron faced with different high-index facets grew in concentric growth mode with almost equal growth rate of growth facets. The unequal growth rate between two neighboring facets caused the new high-index facet to appear, making silicon crystal more roundish. The reason for the formation of nodular silicon crystalNodular silicon crystal with multi-facets was discussed in terms of the discrepancy of diffusion rate of silicon atoms in melt and crystallization rate of silicon grain with changes in temperature. In current study, the high cooling rate in freezing of Al-14wt%Si alloy casting treated by the designed modifier consisting of P, Ti, B, and mischmetal (RE) near the chill mould promotes the occurrence of silicon nodule.

The requirements of lightweighting structures in automotive industry and other transport applications drive the improvement of mechanical propertiesMechanical properties of aluminium alloysAluminium alloys in different manufacturing processes. The present study uses a comparison approach to investigate the microstructureMicrostructure and mechanical propertiesMechanical properties of an Al–Mg2Si–Mg alloy processed by HPDCHigh-pressure die casting and SLMSelective laser melting 3D printing. The microstructure characterisation and mechanical propertiesMechanical properties under as-cast condition and under as-SLMed condition are introduced. The improvement of mechanical propertiesMechanical properties is discussed in association with strengthening mechanism.

AA3104 alloy was fabricated by laser direct energy deposition (DED) additive manufacturingAdditive manufacturing (AM). The high cooling rate contributed to the formation of AlFe intermetallic particles in the melt pool. The heat-affected region along the melt pool boundary contained coarsened Al6(Mn, Fe) and Mg2Si particles. Eutectoid reaction, particle coarsening, and microstructure homogenizationHomogenization can be achieved by post-AMAdditive manufacturing heat treatment. The thermal conductivity of the build substrate was found to affect microstructure development of AA3104 during DED AMAdditive manufacturing, providing opportunities to control phase transformation and particle distribution in AMAdditive manufacturing AA3104.

Aluminum alloyAl wrought alloys development including the proper thermal treatment of materials is a complex matter since many factors, like composition or phase formation amongst others, influence the resulting properties. In the given case, a representative Al–Cu–Mg–Mn alloy was calculated and analyzed. The aim was to relate computational and experimental methods to better understand the processes in the material to come up with better modelling parameters that allow for a more precise prediction of materials properties. Initial equilibrium calculations in Thermocalc were compared to x-ray diffraction (XRD) and scanning electron microscopy (SEM) results on physical samples. This data was used as starting point for precipitation simulation with the Thermocalc Prisma module to calculate the mechanical properties. The experimental mechanical properties determined via tensile testingTensile testing were compared to the computational findings. The correlation between experiment and simulation was then evaluated.

Despite the low solubility and low diffusivity of iron in aluminum, industrial annealing of wrought aluminum is done at or above 340 °C for complete recrystallizationRecrystallization. Cube textured aluminum capacitor foils are annealed at ~220 °C followed by second annealing at 530 °C. This study addresses the underlying cause behind such practices. Pure aluminum samples were pre-strained to ~25%, annealed at 230 °C or higher, cold-rolled, and recrystallized. Iron solute content after annealing at 230–300 °C was 0.014–0.170 ppm and cold-rolled samples were recrystallized to ~1 µm grains at 60 °C. Similar studies were done in AA1100, AA6063, and AA5754. The key finding was at 335 °C, in all cases, either ultra-fine Al6Fe precipitates formed or pre-existing ones dissolved. The relationship between texture evolution and Fe segregation to grain boundaries resulting in solute and particle drag and to microparticles that act as nuclei for de-cohesion will be discussed and smart processing guidelines will be described.

The current study investigated the heat treatmentHeat treatment response of Al–Mg–Si–Mn alloysAl–Mg–Si–Mn alloys with varying Mg/Si ratio. In this regard, Al–5Mg–2Si–0.6Mn–0.15Ti (AMS52) and Al–2Mg–2Si–0.1Mn–0.15Ti (AMS22) alloys were studied. It is found that lower Mg content in AMS22 alloy has caused the formation of ternary eutectic Al–Mg2Si–Si phases. The modification of binary eutectic Al–Mg2Si phases upon heat treatmentHeat treatment is intangible in AMS52 alloy. However, there was a significant modification of the eutectic Al–Mg2Si binary phases in AMS22 alloy. The aging treatment has caused a major improvement in the yield strength of both alloys. Moreover, the AMS22 alloy exhibited a remarkable increase in yield strength (269 MPa) as compared to AMS52 alloy (184 MPa). However, the improved strength in these alloys is achieved at the expense of elongation. TEM results revealed the presence of β′ and β phases in both alloys. The number density of β phases in the AMS52 was much higher than the AMS22 alloy, while the size of β phase is smaller in the former alloy than in the latter alloy. FractographyFractography of tested tensile specimens revealed that the crack is initiated by the fracturing of iron-bearing phases which advances through the debonding of remnant eutectic Mg2Si phases from the Al-matrix.

In the presented work, the effect of heat treatment on the values of the electrical resistivity and the potential level of hardening due to the formation of secondary precipitates of phases of the L12 type of alloys Al–Zr–ScAl3(Zr,Sc) L12 particles system for cold rolled sheets was investigated. By use of the calculated and experimental method carried out quantitative analysis of zirconium and scandium redistribution between the aluminum solid solution and a secondary discharge type L12 after different heat treatment regimes. The positive role of scandium in a more rapid decrease in the values of resistivity in the Al–Zr–ScAl3(Zr,Sc) L12 particles system after heat treatment is shown.

Characteristic and mechanical propertiesMechanical properties and annealing and microstructuresMicrostructure including the transformation of phases, textures, and formability of hotband annealed of a continuous casting (CC) Al–1.5Cu alloy by using tensile machine, optical and scanning electronic microscopes, and X-ray diffraction method were evaluated and studied overall. In addition, the different phases formed during heating were determined by DSC technology. Compared with AA2024, Si and Fe amounts of the alloy were controlled at low level; Mn and Mg amounts were controlled at low limit of AA2024 alloy; Cu is selected at low level (1.1–2.2%) due to the requirement of twain belt continuous cast processingContinuous cast processing. Compared to hotbands of AA5xxx and AA3xxx alloys, material characteristic after annealing at different temperatures of hotband of the Al–1.5Cu alloy is very different with some interesting special findings, such as the precipitation and re-solid resolution of Al–Cu phase as well as forming of P-orientation ({011} <566>) texture and so on. The findings would affect potentially and importantly subsequent processing (such as cold rolling, solid solution heat treatment, quenching, forming, and aging) for application (replace AA5xxx-O sheet) in high strength and low cost auto forming parts or sheets.

Almag 35 (A535) is a commercial aluminum alloy intended for a number of marine components, which is mainly justified by its excellent castability and corrosionCorrosion resistance. However, the most important factor for corrosionCorrosion resistance is the formation of intermetallics that can lead the defects in the oxide film and substrate, as well as activate the corrosionCorrosion reaction. The characteristics of a sealant on the anodic filmAnodic film were investigated in this work. The alloy was subjected to homogenizationHomogenization at 400 °C for 5 h to improve the uniformity of the anodic oxide film due to the decreased number of intermetallics as a result of dissolving in the matrix. It also improved the hardness of this alloy. Electrochemical measurements were conducted to investigate the corrosionCorrosion behavior. The effects of intermetallics and stearic sealing on the characteristics of the oxide layer are discussed. The decrease in the number of intermetallics can lead to reduced corrosionCorrosion current density (Icorr) and increased potential corrosionCorrosion (Ecorr), which results in a lower corrosionCorrosion rate of this alloy.

We have established an industrial methodology for the prediction, formation, transformation, and growth of individual phases in the microstructuresMicrostructure of aluminum alloysAluminum alloys used for the most demanding applications. The thermodynamic calculations of the equilibrium and nonequilibrium states were performed with the Thermo-Calc program, and the microstructure was analyzed with optical and scanning electron microscopy. The effectiveness of the analytical procedure was tested on selected formable alloys from the AA2xxx and AA6xxx series (AA2024, AA2618, and AA6082), where we systematically developed or optimized selected properties of the product. With these advanced thermodynamic and metallographic tools, we can provide our customers with a quality that meets their requirements and creates economic benefits in the form of the higher added value of the finished products and cost savings in the production process.

Hemming is one of the formability-related propertiesMechanical properties which is difficult to describe with the forming limit curve (FLC) and unlike other forming features, its relationship with work hardeningWork hardening behaviour is not known. It is generally known that the formability of Al sheet material is determined by its work hardening behavior up to the onset of strain localization. Under industrial production conditions of a continuous annealing line, the material undergoes various thermomechanical processing steps which can have an adverse effect on work hardening, i.e. natural agingNatural aging, pre-straining, and pre-aging. Therefore, it is essential to understand the evolution of work hardening during these treatments after solution heat treatment and quenching. In this work, the impact of the main post-quench processing parameters of a continuous annealing line on the work hardening behaviour of AA6016 and AA6005 were investigated experimentally by laboratory simulations. Based on the true stress σ–true strain ε curve, the work hardening θ = dσ/dε was characterized by two parameters, namely the initial work hardening rate θ0 and the dynamic recovery rate β = dθ/dσ. The investigation revealed that both parameters θ0 and β decrease most in the course of natural agingNatural aging after solution heat treatment and quenching, but subsequent processing steps also influence the work hardeningWork hardening behavior.

The mechanical properties of Al–Mg–Si alloys are linked to their thermomechanical process history. The objective of this study is to provide a quantitative assessment of the effect of quench rate after solution treatment on the strain distribution at the microstructural level using high-resolution digital image correlation (HRDIC). The microstructure was characterized using electron backscattered diffraction (EBSD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It was found that solute depleted areas formed near grain boundaries are sites for strain localization during deformation.

Lightweight 6xxx aluminumAluminum components are the basis for a sustainable mobility. Therefore, improvements in the thermomechanical processingThermomechanical processing of 6xxx alloys are necessary to further optimize aluminumAluminum structures for the automotive market. Two optimized process routes are presented, which enhance the material's performance compared to the well-established standard process. In the first part, it is demonstrated that an elevated quenching temperature following solution heat treatment of an EN AW 6082 alloy is increasing hardness due to formation of a finer needle precipitate microstructure. TEMTEM imaging showed that the unused solute in-between the needles were clustered, which was calculated to provide an additional hardness contribution. In the second part, a large-scale T8 process involving impact extrusionImpact extrusion and artificial aging of an EN AW 6060 alloy was optimized for a favorable combination of strength and ductility. In this case, the properties were the result of work hardening and preferred precipitation on dislocations.

The current study shows the influence of Sc and Zr element additions in the heat-affected zoneHeat affected zone of 5083 alloy fusion welds. Two different levels of Sc content (called low and high Sc alloys) were studied, while the Zr content of the alloy remained constant. Tungsten inert gas (TIG) welding tests of 3 mm thick AlMg5ScZr alloySc and Zr Alloy sheets in final annealed temper H2X were carried out at Hellenic Aerospace Industry facilities. For comparison purposes, 3 mm thick sheets of a typical alloy 5083 (AlMg4, 8Mn0,5) in temper H321 at final rolling were also welded under the same welding conditions. The filer metal alloy used in all welding tests was of the AlMg5 (ER5356) family. Welded samples were analyzed regarding mechanical and microhardness properties. The heat-affected zoneHeat affected zone microstructure of the weld was studied under light optical microscope. The addition of Sc and Zr in 5083 improves remarkably the microstructure in the heat-affected zoneHeat affected zone. Heat-affected zone recrystallization zone length is reduced significantly in the case of Sc containing alloys, for both Sc levels. On the other hand, the 5083 alloy shows extended recrystallization in the heat-affected zoneHeat affected zone while a coarse grain zone appears adjacent to the fusion area. Such microstructural improvements in heat-affected zone of alloy AlMg5ScZr increase effectively the overall weld strength as illustrated by the mechanical properties of weld.

MacrosegregationMacrosegregation during solidification causes spatial variation of microstructure and mechanical properties in cast parts. This study is aimed at developing a mathematical model to correlate the constitutive behaviourConstitutive behaviour of A356A356 aluminum alloy with compositional and microstructural variations in the as-cast and heat-treated conditions. The model adopts a multiple-input deep neural networkDeep neural network (DNN) methodology to solve the regression problem, which does not require determining a specific form of fitting equation compared to the conventional equation-based method. The model is trained using data generated from a series of casting experiments. The features (input) of the data include the Si content (composition), secondary dendrite arm spacing (SDAS) (microstructure) and heat-treated condition, and the labels (output) include the yield stress and parameters to describe the flow stress. The model was trained with a portion of the available dataset and the output was assessed using the remaining dataset. The results show that the model is capable of accurately predicting the constitutive behaviourConstitutive behaviour.

Automotive stampings undergo complex strain paths during drawing, stretching, and bending operations which develop large plastic strain gradients within the material. Aluminum sheet alloys are increasingly used for vehicle structure lightweighting, but limited formability and high levels of springback present challenges to the manufacturing and assembly processes. The current work explores the springback levels in AA6016-T4 sheet after pure bending operations. Finite element modelingFinite element modeling is performed using both isotropic and elasto-plastic self-consistentElasto-plastic self-consistent (EPSC) model (EPSC) crystal plasticity approaches. The EPSC modelElasto-plastic self-consistent (EPSC) model incorporates backstresses informed by GND content, as measured via high-resolution EBSD. Its predictions are shown to be more accurate than those of the isotropic model. The benefits and limitations of the current EPSC modelElasto-plastic self-consistent (EPSC) model are discussed.

In the present study, the through-thickness functionally graded Al/GNP composite is fabricated by a novel single-step friction stir processing involving a step grooving approach. The digital image correlation technique reveals a variation in localized yield strength from ~44 MPa at the surface to ~49 MPa at the core giving a significant variation of ~5 MPa within a short span of 2 mm (thickness) indicating the higher stiffness of the core region. The maximum strain value also ranges from ~0.79 at the surface to ~0.48 at the core of the composite signifying the strain accumulation near the FSP surface. The load transfer through the clean and semi-coherent interface between the GNP and Al matrix seems to have the dominant role in the localized strengthening of the core region. The property gradient indicates that the objective of fabricating the FGC is successfully realized by the proposed methodology.

We report on a corrosion studyCorrosion study involving different aluminum alloysAluminum alloys from series 2xxx (AA2011, AA2014, AA2024, AA2030, and EN AW 2030) in a 5 wt.% NaCl water solution. The corrosion was investigated using the standard PV113 testPV 113 test and a series of different electrochemical measurements (chronopotentiometry, electrochemical impedance spectroscopy, and cyclic polarization) lasting for 72 h. A possible correlationCorrelation between the maximum penetration depthPenetration depth due to corrosion into the base material, caused by the standard PV113 testPV 113 test, and the time of electrochemical fatigue was investigated. It was found that a linear correlationCorrelation exists between the penetration depthPenetration depth in the base material and the electrochemical fatigue time for most of the alloys tested. Moreover, a correlationCorrelation between the electrochemical fatigue methods and the PV113 testPV 113 test exists for the materials that were the most susceptible to intergranular corrosion. We demonstrated that electrochemical fatigue is suitable for inducing intergranular corrosion.

To promote lightweighting of automotive structures, there is a need for new processing techniques that create a variation in properties within a single component. Such customization would enable optimization of mechanical properties such as strength, ductility, and stiffness thereby reducing the need to specify a material or gage thickness on one region that is not needed in another. To this end, Shear Assisted Processing and ExtrusionShear Assisted Processing and Extrusion (ShAPE) was used to fabricate thin-walled tubing having a gradient in alloy composition, and thus performance, along the length. Tubes that transition from alloy 6061, to 7075, and back to 6061 have been extruded with an outer diameter of 12 mm and wall thickness of 1 mm. Bonding between the alloys appeared relatively sound based on optical micrographs, and few defects were observed using X-ray computed tomography. Very little mixing between the alloys were observed, and the interface between them was very sharp. Hardness in the transition region was nearly identical to the base material, further confirming lack of mixing. Additionally, this work represents the first known thermomechanical processingThermomechanical processing technique whereby alloy 7075 has been joined without creating a weakened heat-affected zone.

RecyclingRecycling allows for the reuse of aluminum with dramatic reductions of the energy, cost, and environmental impact as compared to the creation of primary aluminum from ore. Aluminum is normally recycled by remelting, adding primary aluminum, and casting, all of which be eliminated using Shear Assisted Processing and ExtrusionShear assisted processing and extrusion (ShAPE). Using ShAPEShear assisted processing and extrusion, cold compacted briquettes of 100% AAAluminum alloy 6063 6063 scrap were extruded into tubing with an outer diameter of 12 mm. Tubes underwent T5 and T6 heat treatments and had average strengths meeting T5 and T6 specifications. Briquette preparation methodology affected the properties of the final product, with higher pre-extrusion annealing temperatures resulting in higher strengths on average. Large variability in the data indicates that tighter process control will be necessary to reliably achieve peak strength. The application of ShAPEShear assisted processing and extrusion to secondary scrap enables a 44% reduction in CO2 of the billet material compared to remelt recycled aluminum.

The present work deals with the Shear Assisted Processing and ExtrusionShear Assisted Processing and Extrusions (ShAPE) (ShAPE) of aluminum alloy 2024 tubes and mechanical property optimization via postT8510-extrusionT3510 heat treatmentsHeat treatment (T3510 and T8510). The ShAPEShear Assisted Processing and Extrusions (ShAPE) process enables extruding AA2024AA2024 at an extrusion speed of 7.4 m/min and extrusion temperature of 480 ℃, which is otherwise beyond the extrudability limit of this alloy using conventional extrusion techniques. The ultimate tensile strength reaches 466 MPa for ShAPEShear Assisted Processing and Extrusions (ShAPE)+T3510T3510 condition and 503 MPa for ShAPEShear Assisted Processing and Extrusions (ShAPE)+T8510T8510 condition, both of which exceed the corresponding ASTM/ASM (minimum/typical) values for the studied tube geometry. The yield strength reaches 382 MPa for ShAPEShear Assisted Processing and Extrusions (ShAPE)+T3510T3510 condition and 481 MPa for ShAPEShear Assisted Processing and Extrusions (ShAPE)+T8510T8510 condition, both of which surpass any reported values in the literature or the highest industrial values. In addition, the ductility of AA2024AA2024 tube fabricated from ShAPEShear Assisted Processing and Extrusions (ShAPE)+T3510T3510 or ShAPEShear Assisted Processing and Extrusions (ShAPE)+T8510T8510 are evidently improved by the grain size refinement, second phase refinement, and enhanced uniformity in second phase distribution due to the severe plastic deformation of ShAPEShear Assisted Processing and Extrusions (ShAPE) process.

Cladded tubes are generally used where two distinct properties are required at the outer and inner parts of a tube, for instance, strength and corrosion resistance. In this investigation, shear assisted processing and extrusionShAPE (ShAPE) was employed to fabricate bi-metallic tubes from 1100 and 7075, and 1100 and 2024 dissimilar Al alloyDissimilar Al alloys combinations. Surface defect-free bi-metallic tubes were fabricated via the ShAPEShAPE process. Detailed microstructural characterization of the interface and various locations of the cladded tubes were carried out using light and scanning electron microscopy techniques. A defect-free, metallurgically bonded interface between the cladded layer and high strength Al (7075 and 2024 Al) was observed. Furthermore, hardness and tensile properties of the cladded ShAPEShAPE tubes were examined in the as-extruded conditions.

The aim of the present study is to determine the optimal extrusionExtrusion parameters and heat treatment of the profileProfile made of 5181 alloyAlloy 5181, which ensures the achievement of approximately 25% improved strength compared to the profileProfile made of the 5083 alloy. The influence of the extrusionExtrusion speed, heating temperature of billets, and modes of heat treatment on the mechanical properties of extruded semi-finished products was studied. Preferable fields of application for the 5181 alloyAlloy 5181 are marine, railways, and automotive applications due to the attractive combination of strength properties and cost.

Development of the building and construction and automotive industries sets the task to increase the productivity of equipment and reduce the cost of aluminium extrusionAluminium extrusion. The absolute majority among all aluminium wrought alloys for extrusionAluminium extrusion belongs to Al–Mg–Si alloys (6XXX series). The small additions of Magnesium and SiliconMagnesium–Silicon ratio allow precipitation of metastable phases with Mg/Si ratioMagnesium–Silicon ratio close to 1 during aging, resulting in 5 times higher strength in comparison with pure aluminium. The paper shows the evaluation of the effect of Magnesium–Silicon ratioMagnesium–Silicon ratio on the extrusionAluminium extrusion speed of the developed high-speed 6XXX alloysHigh-speed 6XXX alloys named as MaxiFlow family. Specially developed composition and homogenization parameters of these alloys ensure the increase of extrusionAluminium extrusion speed up to 10–30% compared to the standard alloys. The study of the influence of the content of alloying and impurity elements and modes of homogenization on the phase composition of 6XXX billetsAluminium billets is presented as well as the anodizing responseAnodizing response.

From the experimental observations in continuous anodic currentsAnodic current of the various patterns associated with Low-Voltage Anode EffectsLow-voltage anode effect (LVAE) at the scale of single anodes, a mean of imaging Alumina distributionAlumina distribution anomalies is envisioned under the hypothesis that LVAEs are solely associated with a lack in Alumina. Spatial statistics of the observed LVAEs shape a kind of tomography for Alumina distributionAlumina distribution diagnostics. In the technology studied, characteristic and stable Alumina distributionAlumina distribution inhomogeneities are reported. A signal processingSignal processing approach is devised for automated LVAE detection in anodic time series. High precision and sensitivity are obtained from a training of the level-based change-point detection algorithm using evolutionary optimisation and data carefully screened from voltage, CF4 emissions, and anodic and line current time series. The possibility of detecting a wide range of LVAEs allows one for tracking cell zones recurrently lean. The developed tool is deployed in a private cloud at the scale of full smelters to automate diagnostics in the form of periodic automated reports of standardised LVAE metrics sent to a mailing list of employees involved in the electrolysis process management. The combination of plant data and LVAE distribution confirms the interpretation consensus that Alumina distributionAlumina distribution variability and anomaly is a factor of sub-optimality in the process. This novel capability to draw qualitative mapping of Alumina inhomogeneity paves the way to the development of enhanced feeding mechanisms with spatial intelligence to diminish Alumina variability and improve the process.

Alumina feeding requires optimization for the feed amount, timing, and point feeder locations. The alumina raft formation and dispersion are the essential stages leading to the particles of various sizes travel with the bath flow along anodes in the central channel, in the bath volume beneath the anodes, and gradually dissolving. The raft motion and particles are traced accounting for their inertia, drag in the turbulent flow, the dome-shaped anode bottom shape. Large-scale MHD-driven circulation in the cell is modelled using specific inputs corresponding to real commercial cells of various types. The feed material forming rafts and particles is added periodically, moves with the flow, and gradually dissolves depending on the local turbulence and instantaneous concentration in a location. The newly developed modelling technique is applied to illustrate possible optimization of the feeder locations, the variable mass, and feeding time intervals for possible adjustments suitable for commercial cells.

There are numerous studies published in the literature related to alumina dissolutionAlumina dissolution rate in cryolite melts. However, such studies cover a broad range of results given in various formats. A new empirical equation was developed based on the results of an extensive parametric study using the gravimetric method on alumina disks. A comparison between this model shows large differences from the existing literature. This paper describes and discusses these differences. Most of the variation is caused by three main parameters strongly influencing the alumina dissolutionAlumina dissolution kinetics. First, there is the alumina content and its morphology. Secondly, there is the mass and heat flow around the sample inherent to the experimental methods that were used. And thirdly, the influence of the additives concentration in the bath was identified as a strong contributor to explain the reported differences.

In the Hall-Héroult process, alumina is fed periodically into a cryolite bath, typically forming so-called raftsRafts. While rafts have been observed and sampled in industry, the governing mechanisms for raft formation are not easily assessed in this setting. In this paper, we present a parametric study of alumina feedingAlumina feeding and dispersion, where the liquid is kept close to its freezing point, to which cooled (soluble) particles are added. The effect of the temperature difference between particles and liquid, particle size distribution (PSD), and gas induced convection is considered and assessed. Results from the water model experiments show a strong impact of PSD on the raftRafts floating time. High amounts of fines increased resulting in floating times between 240 and 550 s, compared to 35–135 seconds in the case of coarser particles. Increased temperature and convection contributed positively to dispersion, although less significantly than the PSD.

For the aluminum industry, understanding each step of alumina addition to the electrolysisAluminum electrolysis bath is critical to reach optimal process conditions. From the injection to the complete dissolution, several physical and chemical mechanisms are interacting: solid and fluid mechanics, heat transfer, phase change, and dissolution. The mathematical model presented in this article uses the discrete element method (DEM) to consider the solid alumina powder as a granular material. It is coupledCoupled SPH-DEM model to the “smoothed particle hydrodynamics” (SPH) method to simulate the liquid electrolyte. The second layer of the model is used to calculate the heat transfer and coalescence of solid materials resulting from alumina sintering and bath solidification. Then, phase change is integrated into the model to consider the solidification of the bath. Sequentially, the dissolution of the alumina particles is reproduced and studied to analyse the injection of the alumina in the future.

The behavior of alumina raft at the bath-metal interfaceBath-metal interface in an electrolysisAluminum electrolysis cell has been simulated by a numerical modelNumeric model in a past study. Further improvement on the numerical model led to broader application and a more «cell-like» scenario. The model now considers three distinct bath-metal interface phenomena. First, the transport waveSurface wave stems from disturbances like a gas bubble and alumina deposit. Second, the stationary waveSurface wave is produced by the magnetohydrodynamics force in the cell. Third, a well-known permanent deformation of the bath-metal interfaceBath-metal interface (BMI). Also, the new model simulates the fragmentation and coalescence of multiple alumina rafts. The purpose of this paper is to present an in-depth parameter analysis of the improved numerical modelNumeric model and identify scenarios in which alumina draft aggregates along an axis.

Faster dissolution of alumina is one of the key challenges for improvement of the energy efficiency and production rate increase of Hall-Héroult electrolysis cells. To obtain a faster dissolution, a better knowledge of the phenomena involved in the alumina dissolutionAlumina Dissolution process becomes important. In this work, an alumina sensorElectrochemical Sensor based on the electromotive force principle was applied to measure the concentration of dissolved alumina in a cryolite-based melt from the addition of the alumina throughout the entire dissolution process. Simultaneously, the dissolution process was video recorded. The measurements were performed in a quartz crucible and alumina was added in 1 wt% subsequent additions. Three different industrial aluminas were tested. The general working principle of the sensorElectrochemical Sensor was studied, and the information extracted from the video recordings was used to explain the sensorElectrochemical Sensor results as well as the general dissolution phenomena. The total dissolution time found based on the sensorElectrochemical Sensor results and video recording was compared for different alumina concentrations. The influence of stirring of the melt was also studied.

Producing aluminum alloysAluminum alloys in the Hall-Héroult cellsHall-Héroult cells can be an economical alternative to meet ever-increasing light-weight alloy applications. Alcoa has carried out comprehensive studies over the past years using the Hall cells to produce aluminum–silicon, aluminum–scandiumAluminum scandium alloy, and aluminum–rare earth alloysAluminum rare earth alloy. The studies were performed in 300 A lab scale cells with multiple electrolysis campaigns for each alloy with kilo scale of alloys produced. For the Al–Si, over 7.0% Si foundry alloy was produced by feeding the Hall cell with alumina–sand mixture. For the Al–ScAluminum scandium alloy, a master alloy of 3.5% Sc was produced by introducing scandiumAluminum scandium alloy oxide and alumina. For Al–Re, 8.5% Re alloy was obtained by feeding rare earthAluminum rare earth alloy oxides and alumina. This paper summarizes our lab scale studies for each of the Al alloy systems. Electrolysis operating conditions and key parameters were obtained which are considered a critical step toward commercial application in producing such alloys in the Hall-Héroult cellsHall-Héroult cells.

AluminumAluminum smelters produce pure aluminumAluminum manganese alloys in reduction cells by the Hall-Héroult process but supply a variety of alloys to their customers. The alloys are produced in the cast house, as master alloys containing the desired alloying elements are added to the primary aluminumAluminum from the potroom before casting. In this work, the concept of producing silicon-Silicon or manganeseManganesecontaining master alloys directly in the aluminum reductionAluminum reduction cells, by feeding siliconSilicon or manganeseManganese oxides into the electrolyte, along with the alumina raw material was investigated. The results in this paper are obtained from a laboratory cell, and the current efficiencyCurrent efficiency for the alloy deposition is estimated.

Aluminum smelters produce pure aluminum in reduction cells by the Hall-Héroult process, however, aluminum is usually supplied as a variety of alloys to their customers. The alloys are produced in the casthouse, as desired alloyingAlloying elements are added to the primary aluminum from the potroom before casting. In this work the concept of producing titaniumTitanium master alloys directly in the aluminum reduction cells is discussed, by feeding titaniumTitanium oxide to the electrolyte, along with the alumina raw material. The results in this paper are obtained by running electrolysisAluminum electrolysis experiments in a laboratory cell, and the current efficiencyCurrent efficiency for the alloy deposition is estimated. Similar results for aluminum–silicon and aluminum-manganese alloys are reported in a different paper.

GalliumGallium and germaniumGermanium are practically important trace elements used in various high-tech areas as photovoltaics, electronic equipment, semiconductor gamma-ray detectors, infrared equipment, etc. New secondary raw materials for their extraction are a subject of a thorough search. In this study, new evidence of the presence of germaniumGermanium and galliumGallium in the wastesWastes from the Hall–Héroult processHall-Héroult process was demonstrated and comprehensively discussed, and a method of their extraction was proposed. The concentration of galliumGallium in the carbon dustCarbon dust reaches 0.02% and the concentration of germaniumGermanium is below the detection limit. After the treatment of carbon dustCarbon dust, the concentration of trace elements is drastically increased. The carbon concentrate being a product of carbon dustCarbon dust treatment can be combusted to accumulate galliumGallium in the ash while germaniumGermanium distributes between the ash and the sublimates from the concentrate combustion due to the volatility of monoxide GeO. The concentration of galliumGallium in the ash reaches 0.5 wt.% and the concentration of germaniumGermanium highly depends upon the combustion temperature and the partial pressure of oxygen. The results of trace elements extraction in the acidic and basic environment are shown.

Aluminerie Alouette started in 2017 a project for implementing the AP40 technology at their aluminum smelter in Sept-Iles, Quebec, Canada. Part of this technology consisted of installing a Forced CoolingForced cooling Network (FCN) for regulating the pot thermal balanceThermal balance by cooling down the potshells of their 594 pots. The design of this system was divided into two main components: the pot ductPot duct networks for each pot; and the main collector networksCollector network that provide the required air flow to each of the pot ductPot duct networks. This paper explains the development of this Forced CoolingForced cooling Network from concept design to installation and start-up of the best optimized and efficient solution. An integrated team formed by Alouette, Rio Tinto—AP Technology and Hatch specialists have worked together using a continuous improvement approach to make this project a success.

Based on operation state analysis and energy balanceEnergy balance testing of more than 300 aluminum electrolysisAluminum electrolysis cells in the recent five years, the energy balance characteristics of cells in China was studied. It was shown that the operation state of the aluminum electrolysis cell determined the heat dissipationHeat dissipation. A cell with a good operation state had low energy consumption, the total heat dissipation was relatively small, and energy utilization efficiencyEnergy utilization efficiency was high. For a cell with a good operation state, the regional heat dissipation distribution was good. The excess voltage needed due to the total heat dissipation of a good operating cell was below 1.72 V, and energy utilization efficiencyEnergy utilization efficiency reached above 50%. The regional heat dissipation distribution of a medium performing operation state cell was fairly good, the total heat dissipation voltage was between 1.72–1.82 V, and energy utilization efficiency was 49–50%. Cells with poor operation state generally had a large heat dissipation zone, and the total heat dissipation voltage reached above 1.82 V and energy utilization efficiency was below 49%. This research can provide reference values for energy consumption evaluation of aluminum electrolysisAluminum electrolysis cells and further reduce energy consumption.

In this paper, the variation of liquidus temperatureLiquidus temperature and conductivityConductivity of high potassium aluminum electrolyte with molecular ratio was studied, and the comprehensive energy savingSaving of aluminum electrolysis experiment was carried out in an aluminum smelter enterprise with high potassium electrolyte systemHigh potassium electrolyte system (KF = 5%). The results showed that the superheat of cells was low under the high potassium electrolyte system. When the molecular ratio was controlled in the range of 2.4–2.5, the variation of liquidus temperatureLiquidus temperature and conductivityConductivity of electrolyte was small, indicating that the molecular ratio range was suitable for the actual production process. The energy balance test detected that reducing the side heat loss was the main direction for the enterprise to reduce the energy consumption of the cells. The “Four-Step Treatment Method” achieved the goal of thickening side ledge and reducing side heat loss, and the energy savingSaving of aluminum electrolysis effect was remarkable.

Electrical power outagesPower outages lasting more than 3 h in aluminum smelters often result in shutting down all the cells (pots) in potlinesPotlines. During a long power outage,Power outages the temperature of the molten cryolitic electrolyte (bath) decreases below 900 °C resulting in freezing a large volume of liquid bath which causes a decrease in bath height and anode immersion in cells. When potlinesPotlines are re-energized, there is a substantial increase in the total potlinePotlines voltage due to the higher electrical resistance of partially frozen bath in cells combined with numerous anode effects which often cause rectifiers to trip-out (disconnect) due to power over-loads. The survivability of cells in the potlinesPotlines to continue operating after an extended power outagePower outages depends largely on the corrective actions taken by potroom personnel during the first few hours after electrical power is restored to potlinesPotlines when cells are re-energized. Shutting down potlinesPotlines due to freezing incidents is costly. Some outages can cost up to hundreds of millions of dollars depending on the severity of damages. One of the largest components of losses after potlinePotlines freezing incidents is usually the loss in revenue related to lost aluminum production because of the length of time required to restart all the stopped cells and secondly, the costs associated with repairing or relining costly cathodes.

Power interruptions as well as planned reduction can be difficult to manage due to challenges in thermal balance of the pot. At reduced internal heat, isotherms will shift inwards causing operational difficulties. Additionally, smelters also have pots with different designs and age groups, which react differently to amperage reduction. The study has been performed for a 360 kA potline to run at lower amperages, as low as 280 kA. Hence, computational and analytical models were used by smelter and R&D teams to identify the best cell operating window. The study was used to optimize pot control parameters like voltage adjustment, AlF3 feeding, forced coolingForced cooling modulation pressure, gas suction, metal/bath height, anode cover composition and height, covering/recovering practices, etc. The actions taken at shop floor and control room helped to survive/recover pots during interruptions smoothly.

Good performance in pot preheat, start- up and early operation is key for pot life in long run. However, instances may be encountered where few pots might need to be cut out earlier than expected potlife due to power outage or to abnormal pot condition in early operation or later. Copper-insert collector barsCollector bar have become a requisite for lining design to improve energy efficiency. Restart experience of copper-insert potsCopper-insert pots is different than of pots with conventional steel collector barsCollector bar. Experience in start-up of copper-insert pots is captured in detailed systematic procedures, such as collector barCollector bar resistance measurementResistance measurement, taken on cavityCavity observations cleaned cathode, and pot restartPot Restart economic study estimating the cost of restart and expected pot life to payback. Procedures detailing the activities and parameter changes required during pot cut-in, preheat control and stabilization period during early life are presented in this paper.

TrainingTraining and developmentDevelopment of technical and operational staff, including subject matter and skills competencies, are often undertaken as simple knowledge improvement exercises with success criteria based on information retention. A better approach involves the strategic positioning of trainingTraining and developmentDevelopment linked to business context and purpose. This ensures people understand their personal role in the overall business framework and enables leaders to balance resources (people, plant, and processes), risk, and financial performance. To implement this approach, a structured process with the following attributes has been progressively developed during the implementation of several projects that linked skills developmentDevelopment to business improvement: Using supportive smelter experts to review current plant performance to identify and then quantify technical and financial improvement opportunities. Aligning with senior management on the overall strategyStrategy for the organizational performance changes required to address and deliver identified business opportunities. Developing, agreeing, and implementing inclusive plans to deliver targeted outcomes. Embedding site information and specifics related to the targeted opportunities into trainingTraining and developmentDevelopment actions. Objective and interactive trainingTraining including developing solutions and building confidence. Working within teams to clarify the roles, accountabilities, and authorities required to link and deliver personal results, achieve targeted outcomes, and embed gains. Mentoring, coaching, and providing expert on-demand advice to enhance capability. Sustaining improved performance by verifying individual and team results and then recommending actions to address any shortfalls. The approach demonstrated in this paper is based on experience gained over a number of assignments and is illustrated using case studies from work performed at client smelters to highlight the process and potential benefits.

Process control systems and process simulations of aluminium electrolysis oven performance generally assume a homogeneous electrolyte distribution. In reality, concentration gradientsConcentration gradients in aluminium cells are common due to insufficient mixing. The distribution of carbon particles in the bath was compared between “clean” and “dusty cells”, which were defined as having dust in the tap-hole and anode hole. Simultaneously, physical Anode–Cathode-Distance (ACD)Anode-Cathode-Distance (ACD) measurements were conducted to study a possible association of the anode–cathode distance and the local carbon content in the electrolyte.

In this paper, operation superheatSuperheat of cells, amount of carbon dust,Amount of carbon dust and carbon content in electrolyte were tracked and analyzed for a long time during a period when carbon anode blocks of varying qualities were being used in an aluminum smelter. Electrolyte composition adjustment test was carried out to track and analyse the variations of carbon dust amount and superheat with the variations of KF and LiF contentKF and LiF contents. The results showed that high-quality anodes could significantly reduce the amount of carbon dustAmount of carbon dust and the content of carbon in bath. Reducing the content of KF in electrolyte could improve the superheat and reduce the amount of carbon dust significantly. Anode qualityAnode quality, LiF and KF content in electrolyte, superheat, and carbon content in anode covering materials are important factors affecting the amount of carbon dust produced in the aluminum electrolysis process.

Aluminum reductionAluminum reduction cells have a limited life expectancy, and a significant proportion therefore needs to be replaced each year. This is a large expense for smelters, requiring careful long-term planning. Accurate forecasts can be hard to achieve, however, as they depend on the age distribution, design, and operation conditions of the cells. In this work, we present a statistical model for forecasting the cell replacement rateCell replacement rate. Pots are split into distinct populations, and a statistical distribution is then fitted to each one and used to produce detailed predictions. Special conditions, such as amperage creep, constraints on the start-up rate, or pot euthanasia, can also be taken into account. The model makes full use of the available digital tools: it is easily accessible through a web interface, and directly linked to the relevant databases so that earlier forecasts can be automatically updated as new data becomes available. Potential applications include producing detailed predictions for the coming years, exploring differences across designs or periods, rapidly detecting variations in the life expectancy, and planning replacement campaigns for future cell designs.

In this paper, we demonstrate how we can develop a coarse-grainedCoarse graining model for the alumina distributionAlumina distribution in an aluminium reduction cell. The model is designed to have the potential of being a part of a control system or play the role of a Digital TwinDigital twin. The modelling work is applying the concepts of Pragmatism in Industrial Modelling [5]. The task is to be able to dynamically keep track of where dissolved and undissolved alumina are inside the cell. The numerical grid is the coarsest possible, and special numerical techniques are applied to support fast simulations. The bath (electrolyte) flow is obtained from detailed CFD simulations and imported into the coarse-grainedCoarse graining model. A method to deal with dispersion in such a coarse-grainedCoarse graining model is developed. The physics of particulate alumina dissolution and the electrochemical consumption of dissolved alumina at the anodes are represented. A simple model for the current distribution through the anodes is applied. The model is typically running much faster than real timeReal time. In demonstration simulations, the model runs 50–500 times faster than real timeReal time. From these, it can be observed how alumina particles and dissolved alumina distribute in time and space. Regions where anode effects are expected to initiate can be observed as well as the impacts of changing the feeding pattern and positions for the alumina. The numerical approach is inspired by previous works [9, 10]. The possibilities and limitations of the approach are discussed.

Aluminium (Al) is produced in electrolysis cells that contain two molten, broad, and shallow layers, Al beneath cryolite (bath). A magnetohydrodynamic (MHD) instability known as the metal pad instability (MPI) has been a barrier for reducing anode-to-cathode (ACD) distance and thus decreasing electric losses. The MPI arises from the electromagnetic forces amplifying gravity waves with similar frequencies present at the Al-bath interface. Davidson and Lindsay suggested a mechanical model of the MPI in the form of a compound pendulum with a steady electric current running through it that, in the presence of a vertical magnetic field, couples the pendulum’s motion in the two directions. We expand this model to test whether adding an oscillating (AC) current can stabilize the pendulum’s motion and consequently have the potential to stabilize Al electrolysis cells. We show that AC current can indeed stabilize the motion, and that stability depends in a complicated way on AC amplitude and frequency.

The sulfuric acid dew pointDew point in the flue gasFlue gas from aluminium electrolysis cells increases with increasing concentrations of sulfur dioxide and water vapour. This represents a potential problem in a future scenario with reduced air draught for increased carbon dioxide capture and heat exchangers for cooling or heat collection. A pragmatic model was derived, based on kinetics for the sulfur dioxide to trioxide conversion and models for estimating the temperature and air penetration into the flame. The results indicate that oxidation of carbon monoxide as well as sulfur dioxide takes place mainly less than 10 cm above the crust openingCrust opening. The dew pointDew point increases with decreasing current efficiency and with increasing area and diameter of the crust openingsCrust opening. In the base case, which was thought to be representative of a modern prebake cell, the dew point was 73 °C. The dew point may increase if sulfur trioxide is refluxed with the secondary alumina.

Several technologies for pot gas coolingGas cooling have been developed over the past decade to address detrimental effects such as reduced filter bag life and increased stack emissions from the Gas Treatment Centres (GTCs). In this context, the REEL range of water-cooled pot gas heat exchangers, MHEX, IHEX, and EHEX, have proven to be successful in achieving the required gas coolingGas cooling while providing at the same time GTC capacity improvements. In this paper, we show that these HEXHEX technologies also allow a significant reduction in the plant carbon footprint, either indirectly by utilization of waste heat replacing other carbon-based energy sources, or directly by reducing carbon-based electrical power consumption for the operation of the main fans. Waste heat recovered from the HEXHEX may also enable solutions for carbon capture and storage (CCS) either as a source of energy for the CCS process or as part of the process to concentrate the pot gas with the so-called Pot Gas Recirculation (PGR) solution. Each solution will be discussed, and potential carbon reductions are estimated in the paper.

The alumina electrolyser’s bus barsBus bars, as any other components of the production process, require maintenance, repair, or replacement when necessary. To decrease the voltaic losses caused by poor bus bar interconnections, fusion welding has been used widely. However, the magnetic flux intensity generated by DC current makes fusion welding impossible when electrolysis is operating. On the other hand, even temporary electrolysis shutdown brings along several problems when the process is starting up again. Direct and indirect economical losses relate, for example, to increased energy consumption and decreased lifespan of some production components. This article deals with Friction Stir WeldingFriction stir welding (FSW)—solid-state welding process, as a possible option for weld repairsWeld repair in electrolysis halls during their full operation. Laboratory experiments showed the FSW does not increase the resistivity of welded joints when compared to fusion welding methods. Following pilot repair welding during electrolysis operation employing a developed portable FSW device proved the expected weld quality in terms of weld integrity and resistivity. The possibility to employ the FSW repair of bus barBus bars connections during alumina electrolysisAlumina electrolysis full operation is the most important output. According to conservative estimations, up to 5% of electricity can be saved yearly.

SuperconductorsSuperconductor for electric current have reached a level of industrial readiness, and today in place there are the first superconducting applications and demonstration projects. SuperconductorsSuperconductor are conducting direct current with extremely high densities of more than 500 A/mm2. Further advantages are loss-free high-power transmission, small dimensions of busbarsBusbar, and a low carbon footprint.This paper explains the current steps that had been undertaken to develop an industry-ready technology into real industrial applications for the aluminiumAluminium industry. It explains the design of a 200 kA demonstrator at TRIMET Aluminium SE with the target to complement an existing aluminiumAluminium plant. It covers the following points: The current status of superconducting high-current DC development and its applications; The motivation and an overview of the DEMO200 project at Trimet; The design of a 200 kA busbarBusbar, current lead, and associated connections; The construction and technical layout of currents, magnetic fields, and forces; The test program on how to test a 200 kA system. To close, a conclusive status of the project and an outlook for further applications will be provided.

The metal pad instability (MPI) imposes a minimum electrolyte layer thickness for stable operation of aluminium (Al) electrolysis cells, which limits cells’ energy efficiency. The MPI is a magnetohydrodynamic process that depends on a coupled resonance between hydrodynamic gravity wave modes, driven by the cell’s electrolytic current, appearing as a circulating traveling wave that grows exponentially. Adding an oscillating current component, whose frequency is close to a low-frequency gravity mode instead excites standing waves that can prevent the MPI. Here, we show that a minimum oscillation amplitude is required for preventing the MPI, but excessive amplitude causes a wave that shorts the cell. Proper oscillation frequency choice also impacts the stabilization effect. We also discuss the impact of exciting standing waves on the current efficiency of the cell. Applying oscillating currents could significantly increase the energy efficiency of Al cells without the need for expensive reconstruction paving the way towards more efficient, low carbon Al production.

Baseload energy consumption by primary aluminium smeltersAluminium smelting is rapidly becoming less valuable to power grid operation and stability due to the increasing penetration of variable renewable energy (VRE). For global industry to decarbonize, many smelters must find pathways to reduce their dependence on thermal baseload generation. One such pathway is power modulationPower modulation and the retrofittable EnPot technology can now enable ±20% modulation at any time, allowing smelters to increase the use of VRE in their energy mix, or for them to help firm VRE in national grids. Decarbonizing power systems provide by far the greatest driver to reduce carbon footprints and firming of VRE via smelter modulation is the cheapest way to achieve this, thereby attracting governmental attention and potential funding. A detailed analysis of two energy marketsEnergy markets (coal versus hydro-dominated) shows that beyond the decarbonizationDecarbonization benefits, modulation is also economically advantageous to smelters, and that it opens the door to new contractual scenarios whereby smelters could sell power caps back into the market.

This paper studies a low-temperature aluminium electrolysisLow-temperature aluminium electrolysis charging recovery systemCharging recovery system of a renewable energy cycle power generation systemRenewable energy cycle power generation system, which involves the field of renewable energy and aluminium electrolysis. This article research covers wind power systems, photovoltaic power systems, intelligent integrated power coordination control systems, high-purity aluminium production, low-temperature molten salt aluminium electrolysis charging recovery systems, and aluminium-air battery power generation systemsAluminium-air battery power generation system. The intelligent integrated power supply coordination control system presented in this paper is electrically connected to the low-temperature molten salt aluminium electrolysis charging recovery systemCharging recovery system and the aluminium-air battery power generation system to provide reliable power. Aluminium electrolysis takes place at low temperatures in the range of 700–750 °C whereby the anode is an inert anode producing oxygen gas. The metal is of high purity while the current efficiency is in the 90–95% range. The attached aluminium-air battery power generation systemAluminium-air battery power generation system is used for wind power and photovoltaic power regulation.

The oxidationOxidation of liquid Al–Mg alloysAlMg alloys during holding and casting can lead to issues resulting in poor metal quality and increased dross formation and melt loss. Historically, berylliumBeryllium as a microalloyingMicroalloying element has been used to inhibit the oxidation of high Mg alloys. Due to the negative health consequences, an alternative is desired for berylliumBeryllium. Potential alternative microalloyingMicroalloying elements to Be were investigated in gram and kg-scale TGAs. The effects of Ca, Ce, Ga, Gd, La, Sc, and Sr on the oxidationOxidation of a 5% Mg alloy were investigated in a gram-scale TGA. Additions of Ce, Ga, Gd, La, and Sc were found to have no measurable inhibiting effect on the oxidationOxidation with additions up to 1000 ppm. Ca and Sr showed a potential inhibiting effect and were investigated therefore further in a self-made kg-scale TGA. Sufficient concentrations of Ca or Sr inhibited the transformation from MgO to MgAl2O4 and could be a future replacement for Be.

OxidationOxidation of liquid aluminumAluminum (Al) during processing is a widely known problem, and magnesium (Mg), as a common alloying element, increases the oxidationOxidation rate of the alloy. It has been established that small additions of CO2CO2 (≥ 4%) in an oxidizing atmosphere have a significant inhibiting effect on the rate of oxidationOxidation of Al alloys 5182 (AlMg4.5Mn0.4) and 6016 (AlSi1.2Mg0.4) discs based on oxide layer thickness and mass gain when heat-treated at 750 °C for 7 h. The phases present in the oxide layers for each alloy have now been identified and compared with discs heated in synthetic air and argon (Ar) under the same experimental conditions. The XRD analyses revealed the presence of MgOMgO for all Al alloy 5182 discs, in addition to MgAl2O4 and Al2O3 when heated in synthetic air, and Mg2C3 when heated in the mixed cover gas containing 4% CO2CO2. The low Mg-containing Al alloy 6016 revealed the presence of MgAl2O4 for all discs, in addition to MgOMgO when heat-treated in the mixed cover gas containing 4% CO2CO2, as well as Al2O3 when heated in Ar. For both alloys, Transmission Electron Microscopy (TEM) combined with Energy Dispersive X-ray Spectroscopy and Electron Energy Loss Spectroscopy (EDS-EELS) analyses revealed that the mixed cover gas also resulted in a nanometer-thin amorphous C layer, never previously detected, on top of the thin nanocrystalline MgOMgO layer, retarding the evaporation of Mg and inhibiting the oxidationOxidation rate for both alloys.

Pin hole defects observed in 5182 can lid were found to contain Al–Mg–O spinel inclusions with traces of silica. The lack of calcium and phosphorous in the inclusions suggested they were not from usual refractory sources but could be from dense fused silica (DFS) pins and downspouts reacting with magnesium in the melt. Pin immersion tests, thermodynamic analysis, and SEM (scanning electron microscopy) examinations were carried out to study the mechanism. The thermodynamic analysis and the immersion tests showed that at low magnesium content, MgO forms as the reaction product but at higher magnesium levels MgAl2O4 forms. It seems likely that the reaction products take up more volume than the silica which would cause further spalling of the fused silica and separation from the BN coating. The importance of examining and maintaining the integrity of the BN coating was highlighted to prevent a melt-to-pin reaction. It is speculated that lower porosity pins would be more resistant to attack.

AluminumAluminum thin foilThin foil products are mainly used for food contact materials such as flexible packaging, containers, and household foils. As the thickness of the foil is becoming thinner, the possibility of quality problems occurring is increased. Such issues include holes, pinholes, and scratches. Heterogeneous grain structure, intermetallic compounds, undesirable impurities transferred from ceramic foam filters, and poor liquid metal refining are some of the causes for these quality problems in the thin foilThin foil material produced by the twin roll continuous casting method. In this study, the root causes of the defects such as intermetallic compounds, Al2O3 and SiO2 particles on the aluminumAluminum cast coil surface, and their effects on final product quality were investigated. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used for the characterizationCharacterization of the defects both on the cast coil and thin foilThin foil materials.

The journey from a machine shop to a position of a global leader in Direct Chill (DC) aluminum casting technology began when a distressed father with six mouths to feed purchased a new lathe for the backyard shop housed in the pump house and paid for the lathe by machining components for the lathe manufacturer. Eventually, his two sons, Bill and Frank WagstaffWagstaff, would focus their life visions at the root of two developing technologies: (1) the dawning of computer-controlled machine tools, and (2) the emergence of DC casting equipment to produce semifinished aluminum products, i.e., extrusion ingot and large format rolling slab ingot, as the dominant process after WWII. In doing so, they merged their skills in machine tool design and materials research into a business known and recognized across the world as the premier molten aluminum solidification technology.

Wagstaff, Inc. grew as the manufacturing capabilities developed into mainstream large-scale computerized numerical control (CNC) machining centers, sometimes even ahead of the commercial machine tool manufacturers. This unique capability positioned the leadership to rapidly take on new market opportunities in extrusion ingot, large format rolling slab ingot, and forging ingot as advances in tribology, surface segregation, and heat transfer hit the scientific journals in the 1990s. The development of new technology based on these scientific advances positioned the company to deliver cutting-edge aluminum solidification technology to the curious but cautious aluminum industry well into the next century. Eventually, the technologies grew and developed into concepts that outpaced the comfort of the owners; thus, they sought a suitable long-term industry partner.

In the present study, carbon-bonded alumina filters, normally used for the filtration of steel melts, have been investigated as a potential filter material for the filtration of aluminum. Short- and long-term pilot-scale filtration trials were conducted, and the filter behavior during filtration of aluminum alloy was determined by the use of Porous Disk Filtration Apparatus (PoDFA) for the short-term trials (with the casting alloy AlSi7Mg) and Liquid Metal Cleanliness Analyzer (LiMCA) for the long-term trials with wrought alloy 6xxx aluminum. All applied filters were also investigated after the filtration trial by Scanning Electron Microscopy (SEM) analysis. Furthermore, sessile drop experiments with capillary purification were performed to evaluate the wetting behavior as well as any reactions occurring between the filter material and the aluminum alloy being filtered.

Several methods exist in industry for the measurement of the inclusion content in aluminium, a measure directly related to the cleanliness of the molten metal. In the present pilot-scale study, Porous Disc Filtration Apparatus (PoDFA)Porous Disc Filtration Apparatus (PoDFA) analysis and the Liquid Metal CleanlinessMetal cleanliness Analyser (LiMCA) were used to determine metal cleanliness. Hot-PoDFA samples and continuous LiMCA measurements were taken out both before and after the ceramic foam filter (CFF). Metal cleanlinessMetal cleanliness data obtained from the PoDFAPorous Disc Filtration Apparatus (PoDFA) samples were compared with in situ LiMCA measurements by correlating metal cleanlinessMetal cleanliness data calculated by counts per area in the case of PoDFA with the counts per volume in the case of LiMCA. The comparability of both methods is discussed in the context of filtration theory and the distinctiveness of both systems.

Liquid metal filtration through a ceramic medium has proven to be an efficient way to secure the removal of inclusions and bifilms from molten aluminium. With an increasing focus on recycling of metal values throughout the metallurgical industry, improvements in filter performance and efficiency is currently sought-after but hard to achieve. In the present study, a series of pilot-scale filtration trials have been performed using 30 ppi Ceramic Foam FiltersCeramic Foam Filters (CFFs) (CFFs) with different surface chemistry and roughness. The trials were carried out with a commercial 6xxx aluminium alloy both with and without additions of grain refinersGrain Refiner (AlTi5B1). The filter performance was evaluated by using the change in metal level over the filter to indicate the pressure drop, as well as by analysing LiMCALiquid Metal Cleanliness Analyser (LiMCA) results. Moreover, microstructural analysis by LOM and SEM/EDX were carried out on spent filters, and current filtration theory used to explain the observed results.

A promising strategy for upscaling ultrasonic melt treatmentUltrasonic melt treatment (UST) during direct-chill (DC) casting is through a strategically placed flow management system in the launder. This aims at improving the melt residence time and acoustic pressure distribution, which ultimately optimizes the treatment efficiency. This work focuses on observing the effect of partitions and UST on the resultant grain refinement upon DC castingDC casting of an AA6XXX aluminum alloy with Zr additions. Billets 152 mm in diameter were cast in a pilot-scale DC castingDC casting facility: cases with and without partitions and with and without UST were compared. The effect of partitions on the UST efficiency was quantified through macro- and microstructure observations and supported with acoustic pressure measurementsAcoustic pressure measurement. The positive impact of partitions on the grain refinement upon UST is demonstrated.

The chlorine in-lineIn-line treatment degasser technology is one of the metal treatment methods utilized in the aluminum industry to produce high quality products. However, the chlorine gas used in the system increases the environmental, health and safety (EHS) risks. At Rio Tinto, the chlorine-free salt ACDSalt ACD (Aluminum Compact Degasser) has been implemented to not only mitigate the EHS risks but also improve the product quality. The salt ACDSalt ACD demonstrates better or equivalent metal treatment performance in terms of metal cleanliness, alkali and hydrogen removal compared to the chlorine degasser. The 5xxx and 6xxx alloy products were cast using both degassing systems and subsequently rolled and heat treated for their end uses. In this paper, the metallurgical propertiesMetallurgical properties, such as microstructure, intermetallic phase distribution, and inclusion population, were compared between the products produced with regular and salt degassers. The chlorine-free salt ACDSalt ACD meets all the requirements regarding downstream processing and final product attributes.

Liquid metal temperature at the castingCasting table needs to be strictly controlled to avoid defects and assure process stability during DC-casting. Simple analytical models can provide us with an insight into the temperature lossTemperature loss as liquid metal moves from the furnace through the casting line and could be used to regulate the temperature of the liquid metal entering the casting table. Part of the heat losses come from conjugate heat transfer between refractory launders and liquid metal. Hence, prediction of the transient temperature field in the refractory during casting becomes a critical element in being able to predict the temperature lossTemperature loss in the liquid. In this study, we use a simple analytical model to estimate the temperature field in the refractory due to its contact with the liquid metal. The analytical results are compared with both experimental data from castingCasting trials and simulationSimulation models (1D and 2D).

The design of DC castingCasting lines requires careful consideration of metal temperatures, flow rates, and automated control systems, with particular focus on the startup phase of the cast. While parameters such as temperature losses and flow rates can be estimated, the calculation of filling rates and control systems performance and stability requires the theory of transient two-phaseTwo-phase flows for accurate predictions. A reduced order model, capable of running in real time, has been developed by use of detailed two-phaseTwo-phase CFD simulationsSimulation. With a modular approach, the digital twinDigital twin can be used to analyze different launder layouts/designs, degassers, and filters, and their effect on key parameters such as startup temperature, filling rates, and level control. The use of the digital twinDigital twin in the development and implementation of a new Hycast LPC castingCasting line is demonstrated and its predictions are compared to experimental data. Further use cases such as control system optimization, intelligent process control, and online deviation detection are discussed.

Master alloysMaster alloy for aluminum serve as a source of alloying elements that are essential to tailoring the metal to its many end uses, ranging from automotive to aerospace to structural applications. Presently, aluminum master alloy production is complicated by challenges ranging from high emissions and costs to low yields and productivities. While master alloysMaster alloy are typically produced from oxide, halide, or metallic feedstocks, sulfide chemistry provides a new opportunity to reduce economic and environmental costs via process intensification and increased yields. Herein, we explore the production of aluminum master alloysMaster alloy from sulfide feedstocks through aluminothermic reductionAluminothermic reduction via reactive vacuum distillationDistillation. We present a thermodynamic framework to elucidate the behavior of aluminum as a reductant for sulfidesSulfides, focusing on volatility and gas atmosphere. We demonstrate the production of a 10 wt% manganeseManganese master alloyMaster alloy via aluminothermic reductionAluminothermic reduction of manganeseManganese sulfide, with a manganeseManganese yield of over 95%. Our thermodynamic and experimental results suggest that aluminothermic reductionAluminothermic reduction of sulfidesSulfides is a possible new route for the production of aluminum master alloysMaster alloy.

Meltables such as Remelt Secondary Ingot (RSI), primary aluminum sow, and other shapes must be dry before charging into a furnace containing a molten heel. Any moisture on a meltableMeltable Safety, including condensationCondensation, may cause an explosionExplosion Prevention. Once a meltable has been dried, it may become wet again from condensationCondensation due to environmental changes in the indoor storage area. CondensationCondensation will occur when a meltable reaches or drops below the dew pointDew Point temperature, thus detecting and monitoring real-time changes in the storage environment is vital to prevent molten metal explosionsExplosion Prevention. The Dew PointDew Point Monitoring and Alarm System (DPMAS) concept was developed and finalized in early 2017 and shared within the aluminum industry. The design, operation, and periodic testing of a portable wireless DPMAS that monitors, alarms, and reports environmental conditions to plant employees in real-time is described in this paper.

Some in our industry believe high water vertical direct chill castingDirect Chill Casting pits are less likely to have a molten metalMolten Metal explosion than a low water vertical direct chill casting pit. This belief is very bad and increases danger to workers in our industry. This paper addresses the issue of molten metal explosionsExplosions with special attention to the differences between high and low water vertical direct chill casting pits. Specifically, in my project, I will be looking at the potential damage of molten metalMolten Metal explosion to workers, equipment, and facilities. I argue that high water direct chill vertical casting pits are actually more dangerous than low water direct chill vertical casting pits. In conclusion, this project, by closely examining molten metalMolten Metal explosionsExplosions, sheds new light on the rarely acknowledged issue of hazards associated with high water pits.

Recent decades have seen significant advances in personal protective equipmentPPE (PPE), as well as machine and equipment safeguards, to increase casthouse operators’ safety. As we add more layers and equipment, the risk of heat-related illness increases. Unfortunately, this all too often leads to operators removing the clothing that was designed to protect them, thereby placing themselves more at risk for molten metal contact. In conjunction with this trend, experiments were performed on the dry and wet resistance to heat absorption and water permeabilityBreathability (breathability) of fabricsFabric commonly used in PPEPPE clothing. These results present the greatest ability today of increasing operator comfort.

FurnaceFurnace tending is one of the activities within the casthouseCasthouse which most depends on operators. Due to the large dimensions of melting and holding furnacesFurnace, the equipment used for tending, also of large dimensions, is either mobile and operated by humans or mounted on rails. RoboticsRobotics integration is limited, because standard robots are designed for high speeds with small payloads, while slow speeds at large payloads are required. To overcome these limitations, a custom robot has been designed, integrating innovative features such as portability (onboard energy supply) and high payload capacity. This paper explains how the various design constraints were overcome by designing a custom geometry for the robot.

Every year, about 70 million tonnes of Aluminium (Al) scrap is remelted worldwide in gas fired reverberatory furnaces. The efficiency of the melting process in such furnaces is strongly influenced by human-driven decisions and some furnace issues. SmartMelt is a novel IoT-based platform that combines real-time collection of sensor data, load data, and operator input in a dedicated interface, and a very efficient physical model of the melting process to provide on-line guidance to execute operations at optimal timings while detecting furnace issues and improving operator safety. Integrated into the daily operations of two furnaces of 30 and 70 tonnes capacity for periods of 16 and 6 months, respectively, the system has yielded an increase of productivityProductivity of up to 12% and a reduction of gas consumption of about 11%. SmartMelt successfully detects in real-time deviations of burners performance while also monitoring and recording delays influenced by external factors.

We present a method of automatic, rapid, and frequent chemical analysisChemical analysis of liquid aluminumAluminum, suitable for real-time monitoring of dissolution and evaporation of alloying elements, continuous monitoring of chemical composition during casting, and for similar situations where an instantaneous measurement of melt chemistry is required. The method utilizes liquid-phase laser-induced breakdown spectroscopyLISB and is shown, for the investigated elements, to be comparable in accuracy to conventional off-line laboratory analysis of solid processProcess technology samples cast from the melt. The automated analysis ensures repeatability and improves plant safety by avoiding manual casting of processProcess technology samples.

During the twin-roll castingTwin-roll casting of strips, the heat exchange between the internally water-cooled shells and the metal has a great influence on the strip forming conditions, such as the sump depth, plastic flow, surface and centerline segregations, and run-out temperature of a strip, which determine the strip quality. In this study, laboratory-scale experiments were carried out on the twin-roll castingTwin-roll casting of strips made of the aluminum alloy EN AW-6082 with simultaneous temperature measurementsTemperature measurements at the shell surface and within the solidification-deformation zone. While the shell temperature was monitored with an infrared camera, a 0.5 mm diameter shell thermocouple was passed through the solidification-deformation zone after the thermal steady state was reached. Subsequently, a finite element numerical model of the laboratory-scale twin-roll castingTwin-roll casting trial was developed. An angle-dependent heat transfer coefficientHeat transfer coefficient was fitted to the experimental results, thereby indicating a spatial resolution of the heat transfer at the aluminum–shells interface.

Horizontal Single Belt CastingHorizontal Single Belt Casting (HSBC) (HSBC) is one of the emerging Near-Net-Shape Casting (NNSC) Processes for producing thin stripsThin strips directly from liquid metal. It has been shown to have several advantages compared to the traditional Continuous Casting (CC), and Direct Chill (DC) casting routes. Nevertheless, some process conditions need to be thoroughly controlled to obtain high-quality metal strip material. Two of these relate to the “back meniscus” andMeniscus the metal “backflow” behaviour. In the present research, the effects of the gap clearance between the back refractory and the belt, the belt speed, and the role of contact angle are studied, for the Horizontal Single Belt CastingHorizontal Single Belt Casting (HSBC) of AA2024 Aluminum alloy, using the Computational Fluid DynamicsCFD modelling (CFD) software, ANSYS-Fluent 19.1. Combinations of variables were evaluated, to obtain the optimal set of processing parameters needed to promote “back-meniscus” stability for the HSBCHorizontal Single Belt Casting (HSBC) process for a vertical, single-impingement, metal feeding system.

Applying the concept of “small is beautiful” into a conservative relatively low technology manufacturing sector where the “economies of scale” argument has been used to build ever more so-called efficient process lines is a major challenge. The energy efficiency of the casting process has only been investigated in a limited fashion. The two “Small is Beautiful” projects aimed to introduce a new concept into foundries with regards to the use of their resources. The new philosophy, “small is beautiful”, starts by encouraging the use of high-quality feedstock, only melting what is required and only when it is required. Recycling of internal scrap is not necessarily acceptable but an aim for higher yields is. Applying counter gravity casting methods to improve yield and give enhanced quality is encouraged as is the recovery of low-grade heat from solidification. The present paper discusses the research undertaken and the key findings from the two projects.

Driven by the rapid technological innovation in the automotive industry, automotive parts suppliers are engaged in developing next-generation processProcess characterization control methods that incorporate historical process knowledge and data from online processProcess characterization monitoring. This work examines how the operational parameters and processProcess characterization variability affect die temperature using quantitative data. It was acquired from a series of experiments performed on a commercial low-pressure die castingLPDC (LPDC) processProcess characterization for automotive wheel production. The operational parameters considered include the pressure fill-curve, cooling duration, water flow rate, and environmental temperature. The cooling duration exerts the most significant impact on the die temperature. In contrast, the flow rate of cooling water only slightly influences the die temperature when the flow rate is below 300 L/h. Additionally, there were no noticeable influences caused by adjusting the pressure fill-curve and environmental temperatures in the tested ranges.

Digitisation and cross-linking in high-pressure die castingHigh-pressure die casting technology (HPDC) have developed greatly over the past few years. In modern HPDC cells, almost all parameters are recorded and evaluated with the aim of achieving optimum casting production in terms of quality, cycle time, and energy efficiency. However, the focus of this process data analysisProcess data analysis and recording is particularly on the HPDC system itself and less on the periphery. This leads to possible interactions remaining undetected and avoidable casting defects continuing to occur. Therefore, the so-called tempering process, which is gaining more and more importance due to the shift towards minimum quantity spraying, is investigated in this research work. In particular, the process parameters of all tempering circuits, which change over time, are analysed with machine learningMachine learning, and linked with quality-relevant machine key performance data of the HPDC machine. The resulting prediction functionsPrediction function generate process control options to holistically optimise casting production.

Aluminum alloy A380 is one of the major high-pressure die-castHigh-pressure die casting (HPDC) alloys fabricated in the die casting sector. However, microstructural features such as shrinkage and gas porosityPorosity, entrapped oxide inclusions, change in the morphology of eutectic Si particles as a function of casting location, and the presence of multiple second phase particulates, especially Fe-bearing phases in HPDCHigh-pressure die casting A380 alloy, result in limited ductility, thus, affecting its structural application. However, through proper modification of the as-cast microstructure, it is possible to improve the mechanicalMechanical property performance of alloy A380. In this study, we report the effect of friction stir processingFriction stir processing (FSP), a well-known severe plastic deformation (SPD) and thermomechanicalMechanical property processing tool for selective microstructural modification, on A380. FSPFriction stir processing effectively refines the as-cast microstructure and breaks down the coarse Si particles, creating a homogenized distribution of equiaxed Si particles in the aluminum matrix. Additionally, FSPFriction stir processing eliminates porosityPorosity that acts as crack initiation sites, leading to improved mechanicalMechanical property strengthStrength and ductility.

A key issue in producing high-quality aluminiumAluminium automotive components by the High-Pressure Die Casting process (HPDC) is minimizing the defects. For the HPDC technology, the wall thickness of components needs to be monitored because it dramatically affects the grain size and porosityPorosity appearance. In this work, local squeeze technology is used in aluminiumAluminium high-pressure die casting. The aim is to optimize quality in thick sections of complex geometries, where designers cannot modify components' features and the casting process cannot solve shrinkageShrinkage porosities with the state-of-the-art process control, like intensification pressure or cooling management. The present paper relates to a study of the squeeze pinSqueeze pin effect on HPDC aluminiumAluminium parts, where material homogeneity for leak prevention is a must. Both product and process development for reliable industrialization of the local squeeze technology will be covered, from casting virtual simulation to the metallurgical analysis of the affected area. The affected area was analyzed by means of to understand the local squeeze effect on microstructures.

Among lanthanides, Gd additionGd addition has been expected to show a good achievement in changing the microstructureMicrostructure of the alloys for better performance in high-temperature applications. Nevertheless, there is a lack of information about the casting practice of Gd additionGd addition in terms of holding time and fading effect. In this study, the effective holding time and the fading effect of Gd in AlSi7Mg alloy have been investigated. After minor (0.1 wt. %) and major (0.5 wt. %) Gd additionsGd addition, different holding times in the range from 15 to 200 min were examined. The chemical composition of the molten bath was frequently verified as a function of the holding time. Thermal analysisThermal analysis macro- and microstructural investigations were performed. The results indicate that 45 min of holding time can produce eutectic Si refinement. Longer holding times promote Gd settling leading to grain coarsening and formation of larger eutectic Si flakes.

The requirement for lightweight in automotive and aerospace applications has been the focal point in many studies. Lately, the effect of rare-earth element addition to Al–Si alloys has begun to be investigated in detail. The aim is to establish higher tensile properties with new alloying element additions. In this work, different ratios of Er, Eu, and Dy were added to A356 alloy. T6 heat treatment was carried out with aging temperatures of 145, 160, 180, and 200 C. 10 cylindrical bars were cast for statistical analysis. Weibull distributions were used to check the reproducibility of test results. It was found that Dy addition had made A356 more brittle while Er addition increased elongation at fracture. The toughness and reliability were found to be the highest in 0.1wt% Er-added alloy.

Casting temperature and iron content are among the most important factors in obtaining superior mechanical properties in hypoeutectic Al–Si alloys. An A380 aluminium alloy that is one of the most widespread alloys used in high-pressure diecasting was selected for examining different iron contents and casting temperatures. The alloy with contents of about 0.7 and 1.2 wt% Fe was cast at different temperatures in the range between 680 and 960 °C with 70 °C interval from each other. The outcome indicates that dendrite arm spacing does not change significantly at different cast temperatures or iron contents. From 820 °C in low-Fe containing alloy and from 890 °C in high-Fe containing alloy, the precipitation of harmful β-phase is suppressed. Moreover, blocky or Chinese script α-Fe compounds become the dominant phase throughout the microstructure. The results suggest A380 with lower Fe contentFe content at casting superheatSuper heat temperature of 100 °C would result in uniform microstructure and removal of detrimental β-phase.

Many ofPre-baked anodes the non-destructive testing technologies developed for the evaluation of pre-baked carbon anodes are based on measurements representing the response of the material contained along a specific pathway in their bodies. To assess anode homogeneityHomogeneity based on these data, some ways of interpolating the measurements within the anode volume are required. This paper presents a method to interpolate such measurements to estimate the distribution of properties at different points within an anode’s body, such as the speed of sound. The method is demonstrated first on a set of two- and three-dimensional toy examples, and then on a full-scale anode tested using acousto-ultrasound measurements. The resulting interpolations are cross-checked with the presence of external defects. The technique is promising for understanding the level of isotropy, positioning defects, and also enhancing the probes design for future implementation of NDTNon-Destructive Testing (NDT) techniques.

Rain Carbon Inc. (RCI) operates a central laboratoryLaboratory in the US to monitor Green Petroleum CokePetroleum coke (GPC) and Calcined Petroleum Coke (CPC) quality for six coke calcining plants. With a wide range of different coke qualities, it is critical to provide reliable results to control production and report accurate results to customers. The objective of this paper is to summarize RCI’s laboratory Quality Control (QC) and Quality Assurance (QA) Programs to ensure consistent, high-quality results. The QC program monitors the performance of instrumentation for key analyses. Reference standards and/or control samples are analyzed at a designated frequency. To supplement this, the laboratoryLaboratory added a QA program to monitor total measurement variability including sample preparation and analyst variability. Periodic Gage R&R studies are undertaken to further develop precision limits for each test. The company also organizes global CPC Round Robins which give additional data and provide a valuable service to the industry. All programs are part of RCI’s Quality Management System (QMS), which has been ISO 9001 certified since May 1993.

The aluminum produced in Quebec is the greenest in the world since the electrical energy is produced by hydroelectric power. Nevertheless, aluminum industry continues its efforts for sustainable production and reduction in greenhouse gas (GHG) emissions. At the same time, it is dealing with the reduction in the anode raw-material quality. This necessitates the identification of new raw materials. One option is the partial replacement of petroleum cokeCoke with biocoke which is a renewable material. The biocoke utilization will add value to the side products and help wood industry diversify its operations. However, the biocoke addition decreases the anode quality according to published works. A method was developed to make this substitution possible by the UQAC researchers, and it was tested only with one type of cokeCoke. This article presents the effect of coke typeCoke type on the anode quality when part of the coke is replaced with biocoke.

The cost of low sulfurSulfur calcined petroleum cokeCalcined petroleum coke (LS-CPC) is higher than that of high sulfur (HS-CPC). The trend of increasing CPC cost has been significant in recent years and has independent from metal prices. Since 2004, INALUM has tried to determine the proper blending formula between HS-CPC and LS-CPC to improve production costs, as well as anode performance without disturbing plant operation. INALUM has used various blending ratios for the two types of coke, i.e. 60/40, 85/15 as well as 100/0. The increased presence of sulfur does influence anode quality but through well-managed granulometry and recipe, anode quality is still maintained. By utilizing the 85/15 ratio in coke blendingCoke blending, INALUM has successfully reduced anode production costs by approximately 7%.

The development of rapid and non-destructive measurement methods for green anode quality assessment during production is important for the industry. It would improve process agility and robustness to face increasing variability in the raw materials. A machine visionMachine vision sensor using a combination of image texture methods was used for extracting relevant paste textural features which were used as inputs of a Partial Least SquaresPLS regression model trained on the process variables. Previous work on laboratory anodes demonstrated sensitivity to pitch demand and particle size distribution. This sensor was then tested in a paste plant to assess its responsiveness to the industrial variability. The sensor was found sensitive to the variations in pitch during optimization experiments.

The performance of carbon anodesCarbon anode in aluminium production will depend on both the coke quality (impurities, structure) and the physical properties of the anode (density, permeability, electric resistivity). Here, a set of industrial anodes of different porosity and permeability, and a set of pilot-scale anodes of different calcined petrol cokes (CPC) were evaluated with respect to the anode potential, voltage oscillationsVoltage oscillations, and double-layer capacitanceDouble layer capacitance. Electrochemical characterisation of anodes with different permeability showed that the voltage oscillationsVoltage oscillations due to CO2 bubble formation on the horizontal anode surface was inversely correlated to the permeability, with the highest oscillations observed for dense anodes. Evaluating pilot-scale anodes with different source CPC (1.4–5.5 wt% S), no significant differences were observed for the overpotential in the absence of bubbles. The anode made from isotropic coke showed a significantly higher double-layer capacitanceDouble layer capacitance than the anisotropic anodes, indicating better wetting properties towards the electrolyte.

The carbon blocks used in the process for the primary aluminum production are baked in Anode Baking FurnacesAnode Baking Furnace (ABFs). These large-scale furnaces have two combustion zones: volatile matters contained in the green anodes are emitted and burnt in the preheating zones, and natural gas or heavy fuel oil is injected and burnt in the heating zones. The control of both combustion zones constitutes a major challenge to ensure the safety of the operations, especially when deviations in the refractory condition, process, and/or operations occur. In 2020 a Process SafetyProcess Safety analysis identified two situations where the controls in place were judged insufficient to ensure the complete safety of the operations: blocked flue walls and flooding situations. In 2021, Innovatherm and Rio Tinto decided to co-develop modules capable of automatically identifying those situations and raise alarms, or ultimately shut down the gas injection. In June 2021, the modules have been successfully implemented in the ABFAnode Baking Furnace in Rio Tinto’s Usine Grande-Baie.

The anode baking process produces significant amounts of volatile organic compoundsVolatile organic compounds (VOC) (VOC) and polyaromatic hydrocarbonsPolyaromatic hydrocarbons (PAH). Measuring the full range of these emissions is costly and time-consuming. However, VOCVolatile organic compounds (VOC) and lighter PAH components that exist mainly in gas phase can be measured by simpler means. Establishing a known ratio between the components could enable estimates of the total emissions by following certain proxy components. To document the distribution and time profiles of VOCVolatile organic compounds (VOC) and light PAH components, different sampling methodologies with time resolution better than 30 min were evaluated. Measurements using thermal desorption (TD) tubes, a photoionisation detector (PID) instrument, and a gas chromatograph with flame ionization detector (GC-FID) were conducted up and downstream the gas treatment centre. Removal efficiencies of selected VOCVolatile organic compounds (VOC) were calculated. In addition, dynamics between different gas components during the firing cycle was shown, showing high initial load of light VOCVolatile organic compounds (VOC) just after the onset of the firing cycle while heavier components emerged later.

Process optimization by applying the Industry 4.0 principles is now on the roadmap of most of the aluminium producers. Especially, the anode assembly loop has shown interest. Gradually, the operational technologies required to allow for the introduction of process intelligence are being developed and deployed. Automated stub and butt inspection, anode and anode rod trackingAnode rod tracking are slowly gaining adoption. In the past decade, STAS has implemented anode rod trackingAnode rod tracking systems using a dual marking approach, which are datamatrix codes for automated reading and alphanumeric marking for human-reading. Although the original code implementing technique proved to be effective and robust, it involved to divert the rods from their regular route. To address this issue, STAS has now developed and deployed a new technique based on laser engraving that has the advantage of being easily installed along the aerial conveyor. This opens the door to a wider adoption of the technology.

Anode assemblies typically consist of steel stubs locked into holes in the anode carbon using cast ironCast iron. The contact resistance between the cast ironCast iron and carbon and the necking of the amperage in the anode top contribute to electrical resistance. In the anode assemblyAnode assembly presented here, the cast ironCast iron is replaced by steel shotsSteel shots and the stubs replaced by plates. The assembly is held together with eight L-locks machined into the carbon anode. The steel shotsSteel shots sinter during an anode cycle, but can after an anode cycle be stripped off, crushed, and re-used. The area of the yoke-carbon connection is increased by using plates instead of stubs. A reduction of 50–100 mV in 11 kA anode assemblies was measured. The contact area and therefore the electrical resistance are less affected when changing plate thickness. The heat loss of such an assembly is therefore easier to design. The rodding operation without having to cast liquid iron will be safer. The footprint, investment cost, and operation cost of such a rodding station will very likely be significantly reduced.

To reduce the carbon footprint in aluminium productionGreen aluminium production, bio-based binders are suggested to replace some or all coal tar pitch in the carbon anodes. In this study, bio-bindersBio-binders based on Norwegian spruce and birch woods were produced in a laboratory setup, which were studied in terms of wetting properties towards petroleum coke. The binders were mixed with petroleum coke and baked to three different temperatures. Graphitization of the binders was investigated on pure carbonized binders by XRDXRD. OpticalOptical imaging light microscopy was used to investigate the structures and interactionsCoke/binder interactions between coke and binder after baking. The bio-based binders appeared to adhere well to the coke particles, indicating excellent wetting behaviour during mixing. The opticalOptical imaging structure of the carbonized bio-binder seemed to be affected by strain due to shrinkage of the bio-binder around the coke grain boundaries.

RUSAL’s prebaked anode production has increased considerably using underutilized green prebake anode production at Sayanogorsk, followed by the design and installation of new prebake anode facilities at Taishet and Volgograd that were carried out in-house by RUSAL’s technical team. The key project solutions are advanced designs of Riedhammer-type furnaces combined with a Solios firing system, heavy oil (Taishet), and gas (Volgograd). This is combined with a product Lifecycle Management System (LMS) for monitoring single anode lifecycle from raw materials, production, baking, and the recycled spent anode (RUSAL ETC). The new Volgograd carbon plant has a 104,000 tons/year capacity. In 2020, an open top-type baking furnace (64 sections) was started in Taishet with a 225,000 tons/year capacity. As a temporary measure, green anodes that are made in Sayanogorsk and Volgograd are shipped via rail to the Taishet Carbon Plant until the installation of the new carbon plant is completed. Longer term goals include increasing the Taishet prebaked anode facility capacity further to 1,018,000 tons/year and the Sayanogorsk furnaces to 472,000 tons/year.

A new glueGlue, AD20 AD20++, that does not contain any carcinogenic compounds has been developed to be used at the sides of the aluminum electrolysis pots either against the shell or in between silicon carbide sidewalls and preformed blocks. The glueGlue has been developed to provide for thermal efficiency and to replace SiC mortars, which usually exhibit poor sticking properties during ramming operation or even during pot life. The different requirements and characteristics that are needed to be successfully used in pots will be presented, and the final properties obtained on the new AD20 AD20++ glueGlue will be given. AD20 AD20++ glueGlue has been used at pilot scale with EQUIBRAS equipmentEQUIBRAS equipment, in comparison with some silicon carbide mortars. The trials performed with the EQUIBRAS machine relate to glueGlue or mortar installation and to unsticking tests with pressure measurements. This AD20 AD20++ glueGlue has been installed in several pots and some of the performance dataPerformance data is provided in this paper.

In alignment with EGA’s vision toward testing and adopting the usage of safe materials in it is cell construction and to ensure high safety standards for its workers, EGA has adopted the usage of polycyclic aromatic hydrocarbons (PAH)-free ramming pasteRamming paste in a selected number of potlines in its operating sites in Jebel Ali and Al Taweelah. This paper describes EGA’s journey toward the usage of different ramming pastesRamming paste and presents required testing and evaluation changes prior to changing the ramming pasteRamming paste type. Performance of the latest types of PAH containing ramming pastesRamming paste and comparison of the cell lifeCell life with several PAH-free and traditional pastes used in EGA is also discussed.

The replacement of carbon-based sidelining materialsSidelining materials by ceramics, mainly silicon nitride-bonded silicon carbide, started in the late 80s. The ceramics have higher thermal conductivity and better oxidation- and chemical resistanceChemical resistance. The latter opened up the opportunity of using thinner linings, which again enabled larger anodes and higher productivity due to amperage increase. Alton Tabereaux was a pioneer in establishing quality evaluation for this kind of material by TMS papers in 1993 and 1994. Inspired by his work and industrial needs, SINTEF, sponsored by the Norwegian aluminium industry, started to evaluate and develop laboratory-scale test methodsTest methods in 1994 to be able to rank commercial materials from the global market. In this paper, we summarize our findings regarding material parameters and test methodsTest methods during the last 25 years. Important information for suppliers as well as users of these types of lining materials are given.

Commercial alumina contains Na2O and CaO, which must be “neutralised” by regular additions of AlF3 to the bath in aluminium electrolysis cells. As a result, most smelters are net bath producers. The present paper suggests that part of the AlF3 can be replaced by the condensate formed by partial vacuum vaporizationVaporization of tapped-off bath, thereby reducing the amounts of deposited bath. The condensate may have a composition close to the main evaporation product (NaAlF4), while the remaining bath will be rich in NaF and can be used for replacing soda. Data for vapour pressure and condensate composition are presented. A bath mass balanceMass balance is derived in terms of Na2O and CaO in the alumina, comprising replacement of AlF3 with condensate from produced bathProduced bath. Different process options are discussed, including repeated cycles of vaporizationVaporization and condensation.

Today, spent potliningSpent potlining (SPL) from the aluminium industry is mainly sent to landfills. From a circular economy perspective, and with limited availability for landfill sites in the future, the industry is looking into ways of cleaning the SPL to produce saleable products. Vacuum vaporizationVacuum vaporization was investigated to determine its applicability for removing fluorides from the graphite-rich first-cut SPL. It was demonstrated that vacuum vaporizationVacuum vaporization at elevated temperatures is suitable for the removal of fluorides. The condensate generally contains cryolite and NaF only, in accordance with thermodynamic theory. At the temperatures used, it was impossible to remove CaF2 or alumina from the SPL, due to the low vapour pressure of these compounds. The holding time at elevated temperature and vacuum affected the amount of electrolyte removed. The findings comply with the theory for vaporization of fluoride mixtures.

The implementation of Ready-to-Use Cathodes (RuC®) using copperCopper conductors in the cathodic system not only allowed to fully avoid rodding but also significantly decreased the specific energy consumption, reducing the carbon footprint of the Hall-Héroult process. The basic concepts, the cathode implementation, and the operating figures in smelting technologies ranging from 300 to 600 kA for up to 2.5 years of operation are highlighted. The robustness of the Ready-to-Use design is proven by stable low cathodic resistance allowing energy savingsEnergy saving in the range from 0.15 kWh to 0.40 kWh per kg aluminum. An autopsy performed after 1140 days of operation revealed a fully intact copperCopper bar system. CopperCopper samples were taken from the bars at different locations and chemically analyzed, concluding that most of the copperCopper value can be recovered after its useful life through recycling processes. Based on these positive results, further spread of the Ready-to-Use Cathode technology is expected.

The presence of scale in process equipment during production of aluminium represents a factor that contributes to reduced performance. The scale problem is best known in the oxide transport and operation of gas treatmentGas treatment units. The maintenance cost of removing scale from processing equipment can be significant. Numerous studies have been carried out dealing with the formation mechanisms of scale at various locations throughout the off-gas system, but few definitive hypotheses about factors leading to the formation exist. SulfurSulfur seems to play a more important role than seen earlier. This publication covers different scale types and their possible chemical formation pathways.

Latest International Aluminum Institute (IAI) guideline includes various methodologies to measure total perfluorocarbonPerfluorocarbon (PFC) (PFC) emissions. Alcoa has continued to review those methodologies in selecting and implementing procedures that give reliable sampling and analytical techniques to measure high-voltage, low-voltage, and pot starts PFC emissions from aluminum cell operations. Canister sampling offers the simplest, cost-effective method to estimate total PFCTotal PFC emissions emissions. However, it is important to investigate the sampling duration and frequency that can produce representative PFCPerfluorocarbon (PFC) emissions for reporting purposes. We need to evaluate if the sampling was representative of high-voltage anode effectsAnode effect and how variability of low-voltage emissions could affect the results. Low-voltageLow voltage PFC emissions PFCPerfluorocarbon (PFC) emissions variability was measured using 24 h gas bag sampling. Alcoa has tested the canister sampling procedures and compared GC–MS with FTIR analytical techniques to standardize the methodology with the goal to share the results and learnings within the aluminum industry.

The paper addresses the basic mechanisms leading to the low-voltage anode effectAnode effect (LVAE) as well as the high-voltage anode effect (HVAE) in aluminium electrolysis cells. The root cause of any anode effect is too low alumina concentration at the anode. By statistical treatment based on a Gaussian distribution of the alumina concentration in the bath, it was found that the onset of a HVAE takes place at higher average alumina concentration if there is a large standard deviation. By calculating the anode potential using a pragmatic numerical model, it was found that a LVAE can take place at a part of the anode as small as 0.001 m2, while the rest of the anode is at the normal anode reaction, which makes it extremely difficult to discover. It was suggested that the on-and-off current pattern observed during LVAE can be explained by alternation between blocking of the surface (AE) and normal electrolysis, induced by non-stationary mass transfer of alumina.

Intelligent control and digital technologies are now widely developed to improve the efficiency of aluminum production. The paper elaborates on how a system is based on machine vision with training a neural network to determine the types of violations of the sealing of electrolyzers. Control commands of the system and operational analysis of their support can be used to improve or enhance the environment in a potroomPotroom. The use of machine vision and neural networksMachine vision and neural networks made it possible to reduce by half the time during which the cells are partly sealed, and to reduce AlF3 consumption by 3–5 kg/t Al. The in-house system was successfully tested in EcoSøderberg potroomsPotroom of the Krasnoyarsk smelter. Plans are to deploy the system across all RUSAL’s smelters with Søderberg technology. The next step of RUSAL Engineering and Technology Center is to proceed to develop a machine vision system to improve the environment in PB potroomsPotroom.

Almost 70 years ago, the Chinese aluminum smelting industry had the aluminum production capacity of only 25 kt/year. At present, the primary aluminum smelting capacity is more than half of the world’s production capacity. The great achievements were made from the contributions of the hard-working and competent Chinese scientists and engineers but also from many foreign scientists, especially Norwegian scientists. Among the many Norwegian scientists who have participated in academic exchange in aluminum between China and Norway, Dr. Halvor Kvande has contributed to strengthening the aluminum bridge between China and Norway.

Start-upStart-up and early operationEarly operation of aluminum reduction cellsAluminum reduction cell are very important for cell performance, life expectancy and environment. Several methods of cell start-upStart-up have been used over time, some early methods with no preheatPreheat, but using preheat has been more successful and remains the predominant method today. Ideally, the cell should be preheatedPreheat slowly to uniform operating temperature on the top of the cathode blocks, but in practice, this is rarely achieved and is different between companies. Bath-up and metal addition also follow different approaches from basic, neutral, or acidic bath and metal addition 12–36 h after bath-up. Recently, dry start-upStart-up has also been used. Early operationEarly operation and the time to normal operation in general depend on cathode block grade and are from 2 to 3 weeks to three months. This paper will present different approaches to cell start-upStart-up and early operationEarly operation through time and among companies.

Although modern aluminium smeltersAluminium smelters using 100% green electrical energy generation can achieve on-site emissions of about 2 kg CO2 equivalents per tonne of aluminium produced (t CO2e/t Al), the total global average emissions from primary aluminium production from bauxite mine-to-metal ingot are much larger, about 16.5 t CO2e/t Al. Two thirds of the total average emissions arise because fossil fuels, dominated by coal and to a lesser extent natural gas, are the source of energy used to generate electricity. However, indirect emissions associated with site services and upstream emissions associated with mining, refining, and delivering materials are also significant contributors, and all these are considered in this paper. Arising from this analysis, we question whether the reference target proposed by the Aluminium Stewardship Initiative (ASI) that the on-site direct and indirect emissions from all present and future smelters shall be below 8 t CO2e/t Al by 2030 or earlier, are the appropriate one. Since the global impact is the total mine to metal emissions, this number is what impacts the public, and also customers and downstream users. Surely the numerical value should be changed accordingly on a science based approach.

Flue gasFlue gas recycling and energy recovery provide an excellent opportunity for the aluminiumAluminium industry to reduce the total energy consumption and to prepare for possible future carbon capture and storage or utilisation. Gas recycling enables increased CO2Carbon dioxide concentration and more efficient recovery of heat from the flue gasFlue gas. The present paper addresses some of the challenges with this technology, including increased concentrations of other pot gases such as CO, SO2, and HF and possible increased fugitive emissions due to reduced suction. Increased concentration of CO is particularly unwanted, since it is a lethal compound. Thus, catalytic conversion of CO to CO2 is crucial for HES (Health, Environment and Safety) reasons, and it also increases the amount of collectible heat. However, high concentration of SO2 can pose problems to equipment, including the heat exchanger units, due to the formation of sulfuric acid when the acid dew point is reached.

The TMS Industrial Aluminum Electrolysis (IAE) Course on Theory and Practice has been held sixteen times in eight different countries in four continents since 1996. The location was always selected so that a visit to a nearby aluminum smelter was a part of the program of the course. The background and development of the course and its contents are presented here, and the experience and learning that the instructors have had during the work with these courses are described. It has been a popular course with an average of more than 50 participants. The success of this course has inspired TMS to organize a series of new courses related to special parts of aluminum production. Their main topics are anode technology, control of potline scrubber and fugitive emissionsTMS potline scrubber & fugitive emissions course, and aluminum cast shopTMS aluminum cast shop course.

Solid-state-recyclingSolid-state-recycling processes for aluminum chipsAluminum chips are promising alternatives to energy-intensive re-melting. In order to directly recycle aluminum chipsAluminum chips without the necessity of re-melting, these are pre-compacted and further processed into profiles in a hot extrusionHot extrusion process. The quality of the so-produced profiles depends on the quality of the interface between the single chips, which are linked by microstructural welding. In order to enable a successful welding process, the pathways during the extrusion process have to be long enough in order to transfer enough energy and the encasing oxide layers have to be broken up successfully. Parameters like pressure, shear strain, and temperature influence the quality of the oxide layer breakup. Especially the shear strain can be varied by the material flow and the die. Therefore, this study examines the effects of different extrusion dies on the microstructure and the mechanical properties. The microstructure was characterized using metallographic investigations and could found to form within four different zones depending on the conditions during the extrusion process. The mechanical properties were investigated by means of tensile tests and fatigue testsFatigue tests and could be correlated well with the microstructure, since two different damage mechanisms depending on the specimen position can be distinguished.

Scrap pre-treatments, such as compactionCompaction and thermal de-coatingDe-coating, are standard industrial practices for recyclingRecycling aluminiumAluminium post-consumer scrap. This study compares the recyclability of a coated and uncoated 8111 alloy under the application of compaction and/or thermal de-coating pre-treatments. Sheets of 600 μm thickness were shredded into chips and compacted by uniaxial pressure, moderate pressure torsion (MPT), or MPT at 450 °C (Hot MPT) into briquettes of 4 cm diameter. A subset of briquettes and loose chips was subsequently heat-treated for 1 h at 550 °C, while the other set was left untreated. The effectiveness of the heat treatment for the different compaction methods was examined by mass balance and the internal porosity of the briquettes by computed tomography. Re-melting the samples under molten salt-fluxSalt-flux showed that the coalescence of the coated material significantly improves with the thermal de-coating pre-treatment, especially for the loose chips and briquettes compacted uniaxially. Lower coalescences were obtained for the de-coated MPT briquettes, as a result of an incomplete de-coatingDe-coating.

The SisAl process encompasses the production of silicon (Si) alloysSilicon alloy by reducing silica in slags aluminothermically, using secondarySecondary materials aluminum (Al) raw materials as reductants. Along with the Si alloy, a CaO–Al2O3–(low)SiO2 slag is produced. Alumina-rich slag can be a source for production of High-Purity Alumina (HPA) and Metallurgical Grade Alumina (MGA) or as slag addition for refining of steel. The current research aims to explain key aspects of aluminothermic reductionAluminothermic reduction using Al drossDross, to facilitate upscaling of the process and combining optimal Si- and Al2O3-yield. Three size fractions of Al dross or Al-heel with secondarySecondary materials alumina recycled from dross were reacted with a CaO–SiO2 slag at 1650–1750 °C in two separate induction furnaces with different size and atmosphere. The products' weights and compositions were determined to calculate the Si yield in the aluminothermic reductionAluminothermic reduction process and back calculate the Al content in drossDross fractions. The present work shows that drossDross as reductant in the SisAl process led to varying Si alloys, CaO–Al2O3–(low)SiO2 slags and Si yields, enabling a circular economy perspective for these secondarySecondary materials streams.

Aluminum is an important base metal that is widely used in various industries owing to its excellent properties, such as light weight (2.7 g cm−3), high specific strength, and high corrosion resistance. However, the extraction and smelting process of aluminum from aluminum ore is extremely energy-intensive, such that significant attention is being given to aluminum recycling. Currently, approximately 1/3 of aluminum is supplied from aluminum scrapAluminum scrap. However, the current aluminum recycling by remelting process is a downgrade approach because the alloying elements contained in the aluminum scrapAluminum scrap cannot be efficiently separated hence enriches in the recycled aluminum. The high alloying concentration in the current recycled aluminum limits its application to aluminum casting alloys, which have much higher tolerable concentration for alloying elements than that of wrought alloys. To achieve an upgrade recyclingUpgrade recycling of aluminum, in this study, separation of the silicon and copper, the two most important alloying elements in typical aluminum casting alloys, were carried out by using a molten salt electrolysisMolten-salt electrolysis process.

Incinerator Bottom AshIncinerator Bottom Ash (IBA) originates from incineration of municipal waste. The waste contains a fraction of metal where some is aluminiumAluminium. Unless proper treatment, the bottom ash ends up either in landfills or in best case as building material. AluminiumAluminium recovered from IBAIncinerator Bottom Ash can be recycledRecycling and used as a material in aluminiumAluminium alloy production. This paper describes the characterisation of a typical big-bag of aluminiumAluminium recovered from IBAIncinerator Bottom Ash and delivered to the aluminiumAluminium industry. The big-bag contained 1300 kg of recovered aluminiumAluminium in the form of lumps with sizes between 5 and 50 mm. The content was split and sieved into five size classes. Each size class was remelted with salt, and the oxide content and chemical composition was determined. It was found that both oxide content and alloy composition varied between the size classes. This should be considered when using aluminiumAluminium from IBA as a charge material.

In this work, we aim to formulate an AlSi10Mg alloy from aluminium recovered from IBA (Incinerator Bottom Ash) towards potential applications such as Additive ManufacturingAdditive manufacturing and High-pressure Die CastingHigh pressure die casting. To do this, we use arc meltingArc melting as a fast material screening method and controlled melting technique for alloy production. The overall aim is to develop a scientific foundation and methodology for successful addition of metal waste in the AM and HPDC process, and to establish to which extent the arc melter could serve as a partial emulator in this context. IBA Al within the size fraction 10–15 mm is analysed in this work. The effect of arc meltingArc melting on (un-alloyed) IBA Al and the resulting microstructure and chemical composition is investigated using SEM and EDS analyses. We find that the major impurity elements contained in IBA Al (10–15 mm) are Si, Fe, Mn, Cu, and Zn, however, there are large compositional variations between individual particles. Additionally, IBA Al contains oxides and carbides which must be handled, as these may promote nucleation of defects such as cracks if not removed. We find that arc meltingArc melting does not effectively remove oxides from IBA. Thus, an additional processing step using salt to separate out most of the oxides is necessary. Finally, we show initial microstructure analysis of produced AlSi10Mg from IBA Al. This work demonstrates the initial potential as well as challenges with our procedure for alloy formulation from IBA Al.