TMS 2015 144th Annual Meeting & Exhibition

Particulate reinforced metal matrix composites are confronted with the problem of particle aggregation emerging in the process of solidification. It sharply deteriorates the mechanical properties of the composites. In order to improve the particle distribution, in situ TiB₂/Cu composites were prepared using Ti and Cu-B master alloys in a vacuum medium frequency induction furnace equipped with a rotating magnetic field (RMF). The effect of RMF magnetic field intensity employed on the particles distribution, mechanical properties and electrical conductivity of the TiB₂/Cu composites were investigated. The results show that with the applied RMF, TiB₂ particles are homogeneously distributed in the copper matrix, which significantly improves the mechanical properties and electrical conductivity of TiB₂/Cu composites. The mechanism of RMF may be ascribed to the following two aspects. On one hand, the electromagnetic body force generated by appropriate RMF drives forced convection in the equatorial plane of composite melt during solidification. On the other hand, a secondary flow in the meridional plane is engendered by a radial pressure gradient, thus making a strong agitation in the melt. These two effects result in a homogenous dispersion of TiB₂ particles in the copper matrix, and hence excellent properties of TiB₂/Cu composites were obtained.

The effect of static magnetic field on the length of mushy zone of a single-crystal nickel-base superalloy during directional solidification was investigated. The application of the 1T magnetic field increases the length of mushy zone of the alloy. The reason can be attributed to the increase in the solidification-temperature range.

Application ultrasonic cavitation and high-energy pulses (e.g. detonation) is a promising way of incorporating reinforcing and grain refining particles in composite and master alloys. This paper gives an overview of research performed recently on the development of new technological approaches and materials with the aim to introduce and distribute nanoparticles in the matrix of aluminum alloys. Both types of particles, introduced externally or formed insitu are discussed. External fields are used for making concentrated master alloys, e.g. Alalumina with subsequent introduction of such a master alloy into the melt with the aid of ultrasonic cavitation; or for direct production of nanocomposites. The examples of implementation include Al-based composites reinforced with nanodiamonds, nanoalumina and nanospinel. The efficiency is illustrated by structure and properties characterization. The research is done within a European program on the application of external fields in liquid metal processing Exomet (EC grant 280421).

The paper presents data on the structure, phase composition and other properties of zirconia and alumina powders obtained by electric explosion of wire and plasma-chemical deposition methods. Scanning and transmission electron microscopy reveal that the nanoscale powders are composed of spherical particles and aggregates formed by these particles. X-ray diffraction is used to identify the parameters of the crystal structure of these powders. Specific surface area is determined for all powders by BET method. Powders are used to improve the mechanical properties of aluminum alloys. For the optimization of introduction reinforcement nanoparticles used ultrasonic treatment of the melt.

The solidification of Al-7wt.% Si alloys under the influence of electric current pulses (ECP) through two parallel electrodes at the melt surface is investigated. An effective grain refinement was found if the ECP is applied during the initial solidification period (nucleation and recalescence). The grain size can be gradually reduced, which is likely due to the remelting process of high-order dendrite arms in the mushy zone driven by solute fluctuation and promoted by thermal fluctuation. This fragmentation process is mainly driven by electromagnetically forced convection. The grain refinement does not require the formation of nuclei from a solidified shell near the electrodes, which would result in a grain rain inside the sample.

The influence of pulse magneto-oscillation (PMO) on the solidification structure of 2205 duplex stainless steel (DSS) was investigated. The influences of different treating power on solidification structure were studied by changing the peak current value. The results indicated that PMO treatment can significantly refine the equiaxed grains of 2205 DSS. The as-cast structure without PMO treatment was coarse equiaxed grains. With the increase of the treating power, the grains of 2205 DSS changed into fine equiaxed grains. The grain density increased from 3.5 grains/cm2 to 42 grains/cm2, i.e. the mean diameter of equiaxed grains decreased from 7.1 mm to 1.8 mm. Meanwhile, the grain refinement due to PMO treatment had little effect on ferrite/austenite ratio during the solidification process.

In real situations, convection often plays a dominant role in solidification process. In this paper, the solidification process of steel ingot was studied using ProCAST® software. The temperature field, velocity field and microstructure of steel ingot were simulated under the forced-convection condition (addition of rotation). The results showed that the exerted rotation on the ingot could produce the uniform temperature distribution and refine the grains during the solidification process. When the rotation angular velocity is 5°/s, cooling curve of the feature points appeared a slight fluctuations with a range of 0.3°C. The growth of columnar grain was restrained, and the grain was refined. When the speed increased to 20°/s, cooling curve of t he feature points appeared the drastic fluctuations with a range of 1–2°C. The proportion of columnar grain decreased while the proportion of equiaxed grain increased greatly and the grain was refined obviously.

This paper summarized the previous investigations about the grain refinement of pure aluminum under electromagnetic field (EMF) treatment, including electric current pulse (ECP), pulse magnetic field (PMF), pulsed magneto-oscillation (PMO) and surface pulsed magneto-oscillation (SPMO). Our previous researches mainly considered the exerting-modes, the effective acting stage and the origination of crystal nuclei for grain refinement of EMF. Moreover, the nucleation and grain formation under PMO treatment was experimentally examined simultaneously, and it was found that the temperature field during the solidification of the melt also has an important influence on the grain refinement. The more uniform temperature field in the melt, the bigger fraction of equiaxed grains can be obtained. This paper contributes to well understand the grain refinement mechanism of EMF.

In-situ synchrotron radiography was used to investigate bubble dynamics in a molten Al-10 wt% Cu alloy during ultrasound pulsing. Radiographs with an exposure time of 25 ms were collected continuously during sonication at a temperature of approximately 640oC. The formation, collapse, and movement of bubbles, including parameters such as size distribution were quantified using image analysis. Results show that the average bubble radius is 16.0±0.5 μm, and that the average bubble radius increases linearly with sonication time.

The solidification structure in the continuous casting of SWRCH22A steel billet (240 mm × 240 mm) with Pulse Magneto-Oscillation (PMO) treatment was investigated. The length of columnar dendrites of the billet decreased from 8 cm to 4 cm after PMO treatment, i.e. the area percent of equiaxed dendritic structure zone increased by 30%. Meanwhile, the center shrinkage of billet was significantly modified. PMO supstantially promoted the nucleation near the solid/liquid interface and drove the equiaxed grains to move to the center of the melt. In addition, the growth of the columnar dendrite was restrained owing to the Joule heat induced by PMO, concentrating on the out parts of the billet. The results indicated that the PMO was a promising technique for solidification structure homogenizing in continuous casting of steel billet.

Convective cells due to thermal and solutal gradients above the solid/liquid (s/l) interface lead to instability or freckle formation which generally results in the breakdown of single crystallinity while solidifying superalloys directionally. To overcome this problem, a novel modification of the traditional Vertical Bridgman (VB) technique is utilized. This new Vertical Bridgman technique with a supmerged baffle (VB-SB) makes use of a ceramic baffle that is supmerged into the melt near the s/l interface to decrease the melt height which leads to reduction of natural convection. Crystals of commercial CMSX-4 superalloy have been grown by both the traditional VB technique and VB-SB technique with various withdrawal velocities. Results are evaluated to establish a comparison basis between VB and VB-SB in terms of interface morphology, dendrite dimensions, and segregation.

Super gravity field was introduced to remove impurity element of copper from Pb-3%Cu melt. The samples obtained by the gravity coefficient G≥200, time t≥30 minutes and temperature T=673 K appear significant layers and the copper phase present gradient size distribution along the super gravity. The copper phase gathers in the upper and middle areas of the sample and it is hardly to find any copper particles in the bottom area of the sample with the gravity coefficient G=400, time t=60 minutes and temperature T=673 K. The mass fraction of copper in the tailing lead is up to 7.090%, while that in the refined lead is just 0.204%. Considering that the mass fraction of copper is 3.034% in the parallel sample, the purification rate of lead bullion is up to 93.274% after super gravity treatment. The lead bullion can be high-effectively purified by super gravity.

The influence of surface pulsed magnetic oscillation (SPMO) on the solidification of 30Cr₂Ni₄MoV steel was tested. The experimental results indicated that the SPMO significantly refined the solidification structure and homogenize composition of this steel. Firstly, the rate of equiaxed grains was increased from 25.3% to 59%. Secondly, the position of CET was changed significantly and the average length of columnar dendrite moved from 21.1mm to 7.9mm. Meanwhile the average secondary dendritic arm spacing (SDAS) decreased from 178.4μm to 144μm. Furthermore, the SPMO also had a positive effect on carbon segregation, ratio of which changed from 0.85~1.2 to 0.95~1.1.

Integrated Computational Materials Engineering (ICME) technologies and Accelerated Insertion of Materials (AIM) methodologies have been developed and applied to the design of novel alloys for customized properties to meet performance requirement in critical applications. Genomic CALPHAD databases for multicomponent systems have been developed. PrecipiCalc® simulations were performed to optimize the heat treatment process for alloys which incorporate nanoscale precipitates to achieve required strength levels. The comparison of the simulation results with the experimental observations of the microstructure and phase compositions serves as the validation of the databases and models used in the genomic design. After the success with lab-scale buttons, full-scale prototypes of the innovative alloy designs have been produced to accelerate the qualification and to assess the full potential of the novel material. A newly invented high-strength wear-resistant Co-base alloy, as a replacement for Cu-Be alloys in aerospace bushing applications, demonstrates the ICME-based genomic design and AIM-based methodology, with the use of various CALPHAD tools.

A phase field model coupled with thermodynamic calculation for describing the dendritic growth in pressurized solidification of Mg-Al alloy during squeeze casting has been developed, in which the effects of pressure on the Gibbs free energy and chemical potential of solid and liquid phases, the solute diffusion coefficient, and the solute partition coefficient were considered. With the comparison of the dendritic growth under atmospheric and elevated pressures, the manifestations of the effect of pressure on the microstructure evolution were discussed. The results indicated that the dendritic growth rate tends to increase and the secondary dendrite arms are more developed as the pressure is increased from 0.1 to 100MPa, which showed a good agreement with the experimental results of direct squeeze casting of Mg-Al alloy.

Zn-Zr binary system has been reviewed with various analytical techniques: scanning electron microscope equipped with energy dispersive spectrometer (SEM-EDS), X-ray diffraction. Zn-Zr alloys are prepared by powder metallurgy. In view of results of repeated experiments, ZnZr₃ is found for the first time. The preliminary judgment is that it is high temperature phase of Zr-rich end of Zn-Zr binary system.

Based on the available experimental information, the thermodynamic reassessment of BaO-YO_1.5 system was carried out. The liquid phases were modeled with substitutional solid solution model, the compounds BaYO₂O₄ and Ba₃Y₄O₉ were treated as stoichiometric phases, the BaOss (halite BaO solid solution), (α-Y₂O₃ and β-Y₂O₃ were treated as pure compounds. The existing discrepancies were summarized, and a new assessment was carried out based on the formation enthalpy of two compounds (BaY₂O₄ and Ba₃Y₄O₉). The thermodynamic parameters of all phases were optimized by Calphad method, a self consistent set of the optimized Gibbs energy parameters was derived, which can be safely used to extrapolate into the multicomponent system. Compared with the experimental data and the results in this work as well as the results reported previously, it is demonstrated that the present thermodynamic assessment is consistent with the most of experimental data.

Hollow particle filled composites known as syntactic foams presently find applications in many high temperature, high moisture environments such as undersea drilling and oil exploration because of their low density and resistance to moisture uptake. Carbon nanofibers (CNFs) hold the promise of improving the strength of such composites. Syntactic foams with 1–5 wt.% carbon nanofiber-reinforced epoxy matrix and containing 15–50 vol.% glass hollow microballoons are characterized for environmental degradation using accelerated weathering in a 90°C water bath for two weeks and for residual flexural strength and modulus. The maximum weight gain observed after moisture exposure was 3.5% for the CNF/epoxy and 10% for the CNF/syntactic foam. Strength generally decreased after weathering by up to 69%, with the exception of the composites containing 5 wt.% CNF, which showed an increase in strength. This was attributed to swelling of the matrix leading to improved traction on the fibers.

Using molecular dynamics simulations and dislocation theory, we studied dislocation structure of Cu/Ni (100) semi-coherent interface and its role in nucleating lattice dislocation under mechanical loading. We found that misfit dislocation pattern is dependent on layer thickness. On each interface, there are two sets of edge-type misfit dislocation with the Burgers vector of 1/2<110> and the line sense along <1–10>. The relative position of misfit dislocations at the adjacent interfaces is related to the layer thickness. This is ascribed to two factors, interaction energy among misfit dislocations and the core dissociation of misfit dislocations. Both of them show layer thickness dependence. Under mechanical loading, lattice dislocations nucleate from misfit dislocation lines. Thus, the incipient of plastic deformation of layered Cu/Ni composites in terms of initial yielding stress is dependent on the layer thickness.

Ultralong (NH₄)₂V₆O₁₆·1.5H₂O nanobelts have been synthesized by sol-gel method coupled with hydrothermal method using V₂O₅, H₂O₂ and (NH₄)₂SO₄ as raw materials. The synthesis conditions including temperature, reaction time and amount of ammonium sulfate have been optimized. The chemical phase, morphology and microstructure of the as-prepared products were characterized by XRD, FT-IR, FE-SEM/EDX and TEM, respectively. Typical (NH₄)₂V₆O₁₆·1.5H₂O nanobelts as-prepared are several hundreds of micrometers in length, 50–100nm in thickness and 200nm-1µm in width. Oriented Attachment mechanism was proved to be responsible for the formation of (NH₄)₂V₆O₁₆·1.5H₂O ultralong nanobelts. The proposed approach is a facile and cost-saving method, which particularly fits for synthesis of (NH₄)₂V₆O₁₆·1.5H₂O nanobelts on large scale.

In producing metal matrix composites(MMCs) in the liquid metal process, how to add nonmetallic particles to the molten metal is important as well as how to mix the liquid/particles. In this study, composite gas generator(CGG) process which was developed as a new addition method of nonmetallic particles to the molten metal was used, more particularly, composite gas(inert gas + particles) is produced by feeding nonmetallic particles into a pressurized inert gas tank, in which upper rotor and lower fan are mounted, blowing and dispersing particles around the inside of pressure tank by rotating upper and lower blades. Composite gas with well dispersed particles was supplied into the molten metal of aluminum alloy by mechanical stirring impeller.Aluminum composite reinforced with nonmetallic particles were evaluated with mechanical properties and micro structures.

Diamond-WC-based cemented carbide composites were prepared by microwave hot-pressing sintering and microwave cold-pressing sintering. Density and hardness of samples were measured to determine the mechanical properties of the composites. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were adopted to characterize the microstructure and phase structure. Energy dispersive X-ray spectrometer (EDX) was used to evaluate the composition of the samples. The results indicate diamond-WC-based cemented carbide composites with excellent performance could be produced by microwave sintering, and samples fabricated by microwave hot-pressing sintering exhibit higher density and hardness, more homogeneous microstructure and diamond distribution compared to the microwave cold-pressing sintered samples.

Dy-doped TiO₂ photocatalysts were prepared by sol-gel method combined with spin-coating technique and sintered by microwave. The effects of the sintering temperature, layer number of the coatings and Dy doping amount on the photocatalytic activities of TiO₂ were investigated. The optimal sintering temperature, number of coating layers, and Dy doping amount was 515°C, 1, and 0.3 (wt) %, respectively. Compared with the conventional sintering processing, microwave sintering process significantly shortened sintering time, and restrained Dy-doped TiO₂ particles growing larger.

Magnesium (with density, p = 1.74 g/cc) being ∼ 30% lighter than aluminum and ∼ 70% lighter than steel is an attractive and a viable candidate for the fabrication of lightweight structures. Being the designers’ choice for weight critical applications, extensive research efforts are underway into the development of magnesium metal matrix composites (Mg-MMCs) through various cost-effective fabrication technologies. In recent years, there has been a progressive advancement in utilizing the microwave energy to consolidate powder materials and the present study accentuates the use of energy efficient and environment friendly microwave sintering process to synthesize magnesium based composite materials. The processing advantages of the innovative and cost effective microwave assisted bidirectional rapid sintering technique followed by hot extrusion are first briefly introduced. Subsequently, the properties of various Mg-MMCs (containing micro/nano sized, ceramic/metal/amorphous reinforcement particles) synthesized using this technique are presented. Special emphasis has been made on the commending properties displayed by the nanoparticle reinforced Mg composites (Mg-MMNCs). Finally, an account of on-going research initiatives in the development of novel light weight Mg-composites is highlighted.

Powder-based fabrication of hybrid reactive composites combining bimetallic and thermite endothermic reactions requires a consolidation process that produces dense composites with no reactions among the constituents. Reactive composites 2Al-3CuO-x(Al-Ni) (x = 1 - 4) were fabricated from nano-thick Al and Ni flakes and CuO nanoparticles by ultrasonic powder consolidation and tested for their ignition characteristics in continuous heating. The hybrid bimetallic thermite composites with x ≥ 2 ignited well below the melting point of aluminum, while maintaining large heat outputs. Combining the large heat output of the Al-metal oxide thermite reaction and the low ignition temperature of Al-Ni exothermic reactions in single reactive composites, the hybrid bimetallic-thermite composites are suited for controlled local heating, as in micro-joining, where small, easy-to-ignite, high-output heat sources are required.

Titanium and its alloys have low density, high specific strength, high fatigue strength, and good corrosion resistance. However, today they are underutilized in industry due to their high cost and poor wear resistance. To further improve their properties, TiB- and TiC-reinforced Ti matrix composites (TiB/Ti and TiC/Ti) were produced by the spark plasma sintering (SPS) process. The TiB and TiC distributions in the composites strongly affected their mechanical properties. We focused on how the matrix powder morphology and size affected their properties. Hydride-dehydride (HDH) and gas-atomized (GA) pure Ti powders with different powder sizes were used as a matrix, and TiB₂ or TiC powders were used as a reinforcement. We investigated the microstructures, the tensile properties, and the Vickers microhardnesses of the composites. The ultimate tensile strengths and the Vickers microhardnesses of the composites containing smaller HDH powders were higher than those containing GA powders.

The micro-mechanical behavior of electron beam melted (EBM) Ti-6Al-4V alloy was characterized and compared with the cast Ti-6Al-4V alloy. Micro-pillars with diameters ranging from 1.5–3.5µm were prepared using focused ion beam milling and micro-compression tests were performed using a nanoindenter. The yield strength, hardness, and wear resistance of the EBM Ti-6Al-4V alloy were found to be significantly higher than those of the cast alloy. Fine lamellar structure resulting from higher cooling rates in EBM process contributes to the better mechanical properties.

It has been reported that TiB is one of the most effective reinforcement materials. In this study, TiB-reinforced Ti alloys were sintered by using spark plasma sintering (SPS). Compared with the conventional method, SPS can sinter for a short period of time and at low temperature. TiB is produced by TiB₂ and Ti in the composite during sintering. Three types of Ti-6Al-4V matrix powders were used: hydride-dehydride powders with particle diameters of 45 µm and 25 µm and gas-atomized powder with a particle diameter of 45 µm. TiB-reinforced Ti-6Al-4V alloys were prepared from these powders by SPS. The mechanical properties of the alloys did not depend on the particle sizes but depended on the particle morphologies.

In this study, Al₂O₃ ceramics were fabricated without additives under high pressure (2–7 GPa) at temperature (1000 °C) using nanocrystalline alumina powder with metastable γ-Al₂O₃ phase as the starting material. Additionaly, 10% TiO₂ was added by sol-gel to inhibite the grain growth.

As a result of high carbon dioxide emission and production of dust from quarrying process, utilization of industrial and agricultural wastes as alternative raw materials for cement manufacturing, thus, has a pronounced positive impact on environment. This study aimed at utilizing distinctive powder synthesis techniques to produce cement-like materials from cockleshells, rice husk ash, and alumina waste. Solid-state reaction and solution combustion techniques were employed in the powder processing. The powders were mixed with water, cast and cured for 7 days. Compositional analysis of the synthesized powders as well as microstructural examinations of the cast specimens revealed that all powders and cast specimens had similar features compared with Portland cement. Results from scanning electron microscopy indicated that the cast specimens prepared from synthesized powders yielded phases identical to those of Portland cement.

The dealloying behavior of Al-15Fe (at.%) ribbons in a 5 mol·L_-1 NaOH solution under static magnetic field has been investigated. The as-dealloyed samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) analysis. The results reveal that Al atoms can be leached out from the a-Al(Fe) and Al₁₃Fe₄ phases in NaOH solutions with magnetic field, and the magnetic field can significantly reduce the particle size of the as-dealloyed samples comparing with those from non-treatment dealloying (1093 ± 202 nm). The average edge lengths of these octahedra are 303 ± 67 nm (under 0.25 T), 380 ± 141 nm (0.5 T), 421 ± 187 nm (0.75 T), respectively, implying that an optimized selection of magnetic intensity is helpful to obtain refined Fe₃O₄ particles. In addition, the particle morphology is obviously influenced by magnetic field and the effects were also systematically discussed.

Understanding and predicting how microstructure evolves has become tremendously important to enable optimization of processing for improved properties. It has been demonstrated that nucleation of recrystallization is a highly heterogeneous process which typically occurs at deformation irregularities such as grain boundaries, shear bands, and in particle deformation zones of the rolled structure. In this research, the location of the potential particles stimulated of nucleation (PSN) in the microstructure was considered. It was assumed that particles situated on grain boundaries are more likely to nucleate recrystallized grains than others. The Monte Carlo Potts model has been used to model PSN in hot rolled structure taking into account that the stored energy due to deformation heterogeneities that exist around coarse particles on grain boundaries preferentially leads to nucleation.

The migration and faceting behavior of low angle <100> tilt and mixed grain boundaries was investigated. For measurements on high purity aluminum bicrystals an in-situ technique based on orientation contrast imaging was applied. In contrast to the pure tilt boundaries, the mixed boundaries readily assumed a curved shape and steadily moved under the capillary force. Computational analysis revealed that this behavior is due to the inclinational anisotropy of grain boundary energy, which in turn depends on boundary geometry. The shape evolution and shrinkage kinetics of cylindrical grains with different tilt and mixed boundaries were studied by molecular dynamics simulations.

Grain growth in two-dimensional nanocrystalline polycrystals is modeled by attributing to each structural feature of a polygonal grain an own finite mobility and energy. By considering grain growth as a dissipative process that is driven by the reduction of the Gibbs free energy a general grain evolution equation is derived that separates into four types of possible self-similar growth kinetics, where for each case the influence of grain boundary and triple junction mobilities and energies on metrical and topological properties is studied. We find that the resulting analytical expressions compare very well with results from modified Monte Carlo Potts model simulations taking into account size effects in triple junction controlled grain growth. In addition, the analytical grain size distributions are used for a theoretical description of experimental data obtained in nanocrystalline thin films upon annealing.

Lightweighting materials are increasingly being used by automotive companies as sheet metal components to meet fuel economy targets by the year 2025. Consequently, accurate material model data need to be developed by applying biaxial strain paths with cross-shaped specimens, since traditional uniaxial stress-strain data cannot capture the deformation behavior in complex forming operations. This paper discusses the development of finite element models and verification of these models against experimental measurements. Such verification is the first step in developing procedures for making an optimum cross-shaped specimen design. Computed results of deformation, strain profile, and von Mises plastic strain in two different specimens agree with experimentally measured values along critical paths in the specimens. In addition, simulated results predict correctly the eventual failure location in the samples. Detailed analyses also suggest that specimen thickness has an influence on the eventual mode of failure. Further studies are being conducted to confirm this conclusion.

Appropriately selected and prepared nanofluids have promised improved volumetric absorption for solar energy harvesting. This study explored methods of optimizing a graphite-Therminol VP-1 nanofluid volumetric solar flow receiver. Previous studies provided a means of selecting the optimum physical parameters of a rectangular flow receiver via a 2D analytical model. This model has been extended to include a specular reflective base, which demonstrated improvements in the overall efficiency. The refractive index of the absorbing medium was included, causing a spectral shift of incoming radiation. Smaller nanoparticle volume fractions were therefore required to achieve the optimum efficiency, which was also determined using the extended analytical model. A more realistic numerical model, prepared using Ansys Fluent, indicated that receivers with partially diffuse reflecting bases exhibited higher temperatures near the base, thereby minimizing surface losses and increasing average temperatures. The magnitude of these increases, however, may not warrant the use of these types of reflectors.

APEI and International FemtoScience (FemtoSci) are currently investigating the use of chemical vapor deposition (CVD) nanodiamond films for application in high temperature, high energy density, and high voltage energy storage components. Present state-of-the-art energy storage technologies, including capacitors and electrochemical batteries, are primarily limited to low temperature operation [1]. Due to diamond’s unique electrical and mechanical properties, which include having the highest dielectric breakdown strength (30MV/cm) and thermal conductivity (2000 W/m*K) of any known material [2,3], it is a near ideal dielectric material for advanced energy storage applications. APEI and FemtoSci will utilize their state-of-the-art extreme environment packaging and materials expertise to exploit the extraordinary material characteristics of CVD diamond to develop the next generation of extreme environment capacitors for energy storage applications. This paper provides the underlying theoretical framework, simulation results, and initial prototype testing of novel energy storage components with a nanodiamond-based dielectric material.

A statistical Design of Experiments was carried out on the nanopatterning of Co/Pd multilayers using block copolymer templating and ion milling. The multilayers were patterned into welldefined 30 nm nanopillars. The effect of varying ion mill beam power and etch angle on the coercivity of the resulting nanopillars was studied by response surface methodology. The results indicated that an etch angle of between 50° and 60° was optimal for yielding coercivity greater than 3.5 kOe, starting with a full-film coercivity of 1.5 kOe. A further study of coercivity versus etching time was conducted, resulting in a maximum coercivity of 6.6 kOe. Vacuum annealing of the ion-milled nanopillars were found to yield a significant increase in coercivity, indicating reversal of ion irradiation damage.

Amorphous Silicon nitride (Si3N4) nanoparticles were synthesized by the reaction of SiCl4 with Na-NH3 solution, Silicon nitride (Si3N4) nanowires have been successfully prepared via direct crystallization of amorphous Si3N4 nanoparticles under high temperature in a N₂ flow. The products were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution electron microscopy, and electron diffraction. They are pure a-phase hexagonal single-crystal structures. The nanowires are long and smooth. The formation mechanism of the nanowires appears to be a solid-liquid-solid (SLS) mechanism.

Structure and magnetic properties of nanocrystalline P6/mmm Sm(Fe,M)₁₇C(M=Ga,Si) are presented. Their structure is explained with a model ground on the Sm_1-s(Fe,M)_5+2s formula (s = vacancy rate) where s Sm atoms are statistically substituted by s transition metal pairs. The interpretation of the Mssbauer spectra is based on the correlation between the isomer shift (δ) and the Wigner-Seitz Cell volumes, calculated from the structural parameters. The δ behaviour of each crystallographic site versus Ga/Si content, defines the Ga/Si. The maximum coercivity is obtained for low Ga/Si content for auto-coherent diffraction domain size ≃ 30 nm. This controlled microstructure might lead to hard permanent magnet materials.

Nanostructured Fe₅₅Co₄₅ powders were produced by two methods: a high energy ball milling and a polyol reduction process. All the synthesized samples of FeCo nanoparticles were annealed at 600°C for distinct durations under argon. Structural properties of samples were analyzed by XRD, using the Rietveld method, and by transmission electron microscopy. We showed the formation of a bcc single phase structure for all samples with an average size of 41 nm and 20 nm for nanoparticles prepared by the polyol method and by the high energy ball milling, respectively. No additional peaks were observed which indicates the high purity of the samples. The magnetic measurements of all samples were done using the PPMS system. The highest saturation magnetization of 235 emu/g with a low coercivity of 76 Oe was obtained for the Fe₅₅Co₄₅ nanoparticles synthesized by the polyol process. The Fe₅₅Co₄₅ prepared by high energy ball milling showed only 225 emu/g.

In Li/air batteries, the discharge process and capacity are closely related to the composition of air electrode. Carbon is the main component of air electrode and therefore its intrinsic properties will affect the performance of batteries. It has been found that the discharge product was epiphytic on carbon surface during discharge, and the large mesopores (> 30 nm) or macropores in the carbon were the response site of discharge reaction where the discharge product was stored. These have also been confirmed by comparison with ideal electrode composed of carbon nanotubes (CNTs).

In order to improve the properties of electrolyte solution for the nickel-zinc battery, the affection of the KOH and seven kinds of important additives (LiOH·H₂O, KF·2H₂O, K₂CO₃, (CH₃)₄NOH, C₁₉H₄₂BrN, (NaPO₃)₆, ZnO) on electrolyte solution performance is investigated with the experimental Uniform-Design method. The relationship of the electrolyte composition and the solubility of discharged products of zinc are determined by EDTA titration method; the effect of different electrolyte composition on corrosion of zinc is characterized by determining the hydrogen evolution volume. Based on regression analysis, the main influencing factor can be obtained. The best proportioning of electrolyte additives is gained by the multivariate regression fitting, on condition that the solubility and the velocity of hydrogen evolution are regarded as response variables. The optimal formula is as below: 41g KOH, 12g K₂CO₃, 0.15g (CH₃)₄NOH and 0.36g C₁₉H₄₂BrN per 100ml of electrolyte solution.

Anodized aluminum oxide (AAO) thick films with numerous nanochannels have been exfoliated mechanically by the pressure of hydrogen gas generated at the interface between an oxide layer and a metallic aluminum during the subsequent cathodic reduction process after growing of anodic aluminum oxide layer. Co/Cu multilayered nanowires with alternating Co and Cu layers of 10 nm in thickness have been electrodeposited into extremely long nanochannels of AAO films with 60 µm in thickness. Average growth rate of the multilayered nanowires is around 18.2 nm sec-1 and the cylindrical shape is precisely transferred from the nanochannels to the nanowires and the aspect ratio reaches up to ca. 1,000. Co/Cu multilayered nanowires with diameter 60 nm are easily magnetized to the long axis direction of nanowires due to the uni-axial shape anisotropy. 30% of current perpendicular to plane giant magnetoresistance effect has been observed in the multilayered nanowires with 6,000 Co/Cu bilayers.

ZnTe compound semiconductor thin films have been synthesized using an electrodeposition process from an acidic aqueous solution. The film thickness of electrodeposited ZnTe is around 3 µm, and the growth rate is ca. 3 nm sec-1. Optical absorption of ZnTe thin films has been observed in the wavelength range less than 559 nm. The band gap energy of annealed ZnTe thin films is ca. 2.3 eV, which is close to the value of ZnTe bulk single crystal. Electrical Resistivity of ZnTe thin films has been measured using a sample exfoliated from a conductive ITO coated glass electrode. The resistivity of as-deposited ZnTe thin films is ca. 106 Ωm, whereas the resistivity of annealed ZnTe thin films is around 104 Ωm, which is lower than the value of ZnTe bulk single crystal.

In order to research the performance of platinum nanowire array electrode for electrocatalytic oxidation of methanol, anodic aluminum oxide (AAO) film was used as template to prepare platinum nanowires at first by alternative current (AC) electro-deposition. The morphology, elemental composition, micro-structure of Pt nanowires was characterized by SEM, TEM, SAED, EDS, XRD and XPS. The results indicated that the diameter of Pt nanowires was about 70nm, the nanowires were solid line without break, and their radial surfaces are not smooth. In addition, they are crystal structure and in the metallic state.

The aim of this work is to study the dielectric properties of thin films of tungsten trioxide. WO₃ is an interesting material in the field of gas sensors. Here, we investigate the dependence of the electrical conductivity with temperature as well as the effect of the pressure on the thermal activation energy. For this purpose, we have used Impedance Spectroscopy (IS) to study the dielectric properties of RF sputtered WO₃ thin films. Particularly, we have emphasized the effect of oxygen pressure on the surface conductivity.

Performance metrics for parts made using Additive Manufacturing (AM), such as inter- and intra-layer strength, are a function of the energy source, scan pattern(s) and material(s). Similarly, residual stress, surface finish and part distortion are a function of the state change of the material(s), scan pattern(s), overall geometry and post-fabrication steps.A brief overview of newly developed computational tools for metal based AM to simulate performance metrics along with their experimental validations are discussed in this paper, including five major areas of AM simulation. These five areas are: (1) thermo-mechanical constitutive relationships for process predictions during fabrication and part predictions in-service, (2) the use of Euler angles for gauging static and dynamic strengths, (3) the intelligent use of matrix algebra and homogenization to extract the spatiotemporal nature of AM processes, (4) a fast GPU architecture and (5) agorithms targeted towards attaining an accurate faster than real-time simulation efficiency.

This paper discusses the modeling challenges related to additive manufacturing in general and DMLS (Direct Metal Laser Sintering) in particular. A seamless coupling of length scales allowing detailed analysis of the melt pool, laser track, material deposition and resulting residual stresses is presented.The modelling components are verified separately and the complete modeling process is validated against experimental measurements. Comparison of numerical predictions and experimental measurements show good agreement. Finally, as a practical demonstration of the modelling platform applicability to improved work piece quality, the numerical optimization of deposition tracks to reduce in build residual stresses is demonstrated.

This paper presents an overview of the possible micro and macrostructural effects that selective laser melting has on aluminium-based alloys. The paper will show how controlling the melt pool both in terms of delivered thermal energy and morphology can affect the state and composition of deposited material which is correlated to the final micro-structure produced. In addition, the paper presents the use of nondestructive evaluation techniques such as micro-CT as a quantitative method for understanding the effects of the process conditions on a component’s final quality. Mechanical characterisation such as nano-indentation will also show the compositional effects across individual weld pools and contribute to the discussion on how to best control such additive manufacturing method for high quality final component manufacture.

Weld transition joint between modified 9Cr-1Mo steel (P91) and austenitic stainless steel (AISI 304) was developed applying solid state friction surfacing method. Inconel Alloys 625, 600 and 800H were deposited as interlayers in between P91 and AISI 304 to obtain a gradual change in coefficient of thermal expansion. The post weld heat treated (750 ºC/1hr/air cooling) samples were subjected to stress rupture tests at 600 and 650 ºC with different stress levels. The multi-layered coated weld transition joints showed improved stress rupture lives compared to the single layer coated joints. The results were discussed in terms of the microstructural changes.

The laser powder-fed additive manufacturing (AM) of Alloy 625 (UNS N06625) on two heat-treatable, high-strength, and copper-rich alloys, such as Monel K-500 (UNS N05500) and Toughmet 3AT (UNS C72900), has been investigated to determine the suitability of AM for the repair of high-value oilfield parts requiring good machinability, magnetic transparency, anti-galling resistance, and general corrosion resistance. In contrast to conventional laser cladding, AM deposition rates can be greatly reduced to minimize thermal effects, chemical dilution, and number of powder-fed deposits, while still producing a top surface that fully meets Alloy 625 specification. This paper presents and discusses test results from microstructural analyses, chemical composition, electron-backscatter diffraction (EBSD), and microhardness indentation measurements on both Monel K-500 and Toughmet 3AT.

Selective laser melting (SLM) is an additive manufacturing (AM) technique to produce complex parts. However, Ti-45Nb (with a low stiffness as well as an excellent biocompatibility and corrosion resistance) is not yet developed by this process towards biomedical applications. Therefore, this work is to analyze SLM Ti-45Nb with an engineered content of porosity. It is shown that the combination of porosity and the material property can lead to an elastic modulus within the range observed for a bone. The matrix contains only a β-phase after laser rapid solidification. The β-phase is composed of larger laser solidified grains embedding numerous submicron/ultrafine subgrains. The ultrafine subgrains enable a high ductility in conjunction with a satisfactory compressive strength (despite the presence of porosity). The SLM full melting, assessed by the shear strength evaluations, also contributes to the satisfactory mechanical strength. The findings are very promising to benefit biomedical implants for load-bearing applications.

In additive manufacturing (AM) the moving heat source and layer deposition gives rise to each volume of material receiving a complex thermal history. In addition, the machine control systems can vary the heat input as a function of the component geometry and process themes. Together, this can potentially cause both short and long range microstructure heterogeneity, which can potentially impact on the local mechanical properties of AM components. To systematically quantify the heterogeneity typically seen in the lamellar microstructures found in AM titanium parts, a tool has been developed that combine’s automatic high resolution SEM image mapping with batch image analysis, to enable efficient quantification over large areas at the required resolution. This method has been applied to parts produced in Ti6Al4V by selective electron beam melting using an Arcam machine. The method and test cases are described, where both long and short range heterogeneity have been identified in samples and correlated to the build parameters.

With Ti alloys like Ti-6Al-4V, the solidification conditions across virtually all AM platforms lead to strongly textured, coarse columnar, β grain structures. Transformation to α on cooling dilutes the texture, but significant texture is still inherited which contributes to undesirable anisotropy in AM parts. In the work presented a deformation step has been integrated into the manufacture of components produced by the blown powder method, using an Ultrasonic Impact Treatment (UIT), which has the additional benefit of reducing residual stresses. It has been found that the introduction of surface deformation to each layer can lead to a greatly refined grain structure with a more randomised texture. To investigate the origin of this effect, reconstruction of the β grain structure and texture from the α EBSD measurements has been used to characterise the high temperature β microstructure.

Wire arc additive manufacturing (WAAM) is a flexible and high deposition rate technique for production of a wide range of components. Limited available composition of feedstock (wires) inhibits experimentation aimed at production of high strength parts, particularly for aluminum alloys. In this work, alloy 6061 wires were produced by friction extrusion and subsequently used as the feedstock in a Gas Tungsten Arc additive process. Deposits as thick as 15 mm were evaluated in terms of microstructure, defect content, and strength (via sub-scale tensile testing). Strength and hardness were evaluated both before and after post build aging treatments.

During cladding, the heat input from a new overlay can induce metallurgical changes in the previously deposited layers and change their mechanical properties. This effect is encountered during cladding repair of tooling with robotic pulsed arc (RPA) and was the target of this study. The alloy used for cladding was Maraging 250 steel, an age hardenable 18% nickel alloy. A parametric study was undertaken to correlate between cladding with and without cooling of the substrate and the resulting mechanical properties. Twenty layers of Maraging 250 were deposited (a) with forced air cooling to below 250°F (b) with thirty seconds hold time between layer w/o temp control (c) with water-spray cooling to below 250°F, resulting in an average hardness of 42.2HRC, 51.8HRC and 39.1HRC respectively. A fourth block was deposited cold by forced cooling between passes to below 250°F and was subsequently aged at 900°F for three hours and air cooled. The hardness of this specimen ended at 49.5HRC, as anticipated. For die repair with Maraging 250, temperature control during deposition is therefore desirable, to target a hardness range of 42–44HRC. This hardness range provides a satisfactory combination of elongation strength and toughness for tooling application.

In this study, the microstructures of Inconel 718 fabricated from the selective laser melting (SLM) process were experimentally investigated. Specimens with different build heights were prepared for microstructural observations by optical microscopy and scanning electron microscope. In general, columnar γ dendrites are found along the build direction from the X-plane (side surface), while the microstructure of Z-plane (scanning surface) is characterized by equiaxed grains. The microstructures vary along the build height; the top layers present coarse columnar dendrites while the bottom layers show much narrower and uniformly distributed columnar dendrites owing to a very high cooling rate. The top layers also present the combination of a γ matrix and a higher percentage of the Laves phase. On the other hand, the bottom layers show a much less Laves phase due to, again, a higher cooling rate.

Femtosecond laser-based machining shows great promise for micro-scale specimen fabrication as this technique combines fast and precise milling while minimizing surface damage. Whereas focused ion beam (FIB) based micromachining techniques achieve milling rates smaller than ~1 µm3/s, femtosecond lasers can achieve milling rates up on the order of 103 µm3/s, allowing for high throughput specimen fabrication and experimentation. Utilizing only a femtosecond laser and a precison three-axis positioning stage, microtensile specimens were created with gauge widths less than 50 µm from bulk metals.

The annealing procedure is crucial to promote the quality of Al-killed steels, which are widely used in the automotive industry. The continuous annealing (CA) has a potential to replace the batch annealing (BA) due to its benefits of higher efficiency and energy saving. Unfortunately, the yield point phenomena would be easily induced during the mechanical process after the treatment of CA. The tensile behavior, the grain size and the interstitial atom quantity of BA or CA treated samples with and without aging treatment were investigated to understand the reason for appearance of yield phenomena. Tensile tests showed the yield point was observed in the CA sample after aging treatment. Atom probe analyses presented that the content of interstitial carbon atom are very low in both BA and CA samples. Additionally, the grain size of BA sample is larger than CA. Finally, the reason of yield point appearance is discussed.

In this paper, a representative volume element (RVE)-based multiscale approach was proposed to evaluate the bulk deformation of a special casted stainless steel (SS316L). The microgeometry of the casted SS316L specimen was obtained by a non-destructive X-ray computed tomography (CT) system. The geometrical RVE models were constructed based on the size, spatial distribution and volume fraction of micro-voids from the processed CT images. Commercial finite element (FE) package ABAQUS was employed to simulate the compressive deformation of RVE models. Since the inhomogeneity of the RVE was taken into account in the entire specimen, micro-voids inside the specimen were replaced by matching RVE models and the predicted flow stress data of the specimen were compared with the experimental results and hence the proposed RVE-based multiscale method has been verified.

The deformation twinning behavior in Cu-Ni-Si alloys strengthened by Ni₂Si precipitates have been studied. The SEM/EBSP result indicated that the nano-scale deformation twins cannot grow to micro twins during room temperature deformation. The results also revealed that the formation and growth of deformation twinning needs certain strain and stress level in the alloy aged at 723 K for 3.6k and deformed at 77 K. In contrast, it started from initial stage of deformation in the alloy aged at 723 K for 64.8 ks and deformed at 77 K. These results indicate that the deformation twinning needs certain level of stress rather than strain in precipitate strengthened Cu-Ni-Si alloy.

Magnesium and its alloys are widely studied for use as biodegradable temporal implants. The resorption rate of the Mg based implant depends on the orthopaedic application. This rate and the mechanical properties should match the body requirements. Thus silver (Ag) and Gadolinium (Gd) have been chosen as alloying elements to tailor the biodegradation of the material in an application specific way. Ag accelerates the degradation and is used as antibacterial agent and Gd is reported as a slow degrading alloying element and improves the mechanical properties.This work focuses on the comparison of as-extruded samples of Mg-Ag (2w%, 4w%, 6w%) and Mg-Gd (5w%, 10w%) with known materials such as pure Mg and Mg4Y3RE in two different media: phosphate buffered saline (PBS) at 37°C and Dulbecco’s modified eagle medium (DMEM) with 5% CO₂ at 37°C. Hydrogen generation and mass loss in immersion tests are compared and also electrochemical methods are applied. Each testing condition leads to different degradation behaviour. In PBS a clear difference between fast and slow degrading samples is noticeable, however in DMEM there is no significant difference.

Open-porous structures from ß-type Ti-45Nb, as a new biomaterial with an excellent biocompatibility, are produced by selective laser melting (SLM). However, the products commonly suffer from uncontrolled surface issues such as staircase effect and non-melted (or partially fused) powder particles (originating from the SLM production stage). This work is to resolve these issues by modifying the chemical etching protocol, used for surface modification of Ti-based porous structures, by adding a preliminary thermal oxidation step. It is found that a successful removal of non-melted and partially fused powder particles can be achieved through the modified surface treatment protocol. The etching also decreases the surface roughness alternations of the struts as an inevitable consequence of the SLM process. These improvements are accompanied with side effects such as excessive strut thinning and preferential material removal at nodal zones. This, however, may be resolved through improving the design at the production stage.

Titanium biomaterials are widely employed to produce medical components, such as prostheses, plates and screws or dental implants. Their diffusion is ascribed to the broad spectrum of optimal mechanical and surface properties, such as the corrosion resistance and correlated low ionic release, the bio-compatibility, and especially, the enhanced osseointegration that can be achieved by surface modifications, particularly by suitable anodizing treatments. The anodic oxidation technique consists of polarizing titanium by imposing a current flow between the titanium specimen and a counterelectrode. The process parameters which most determine the properties of the growing oxide are the electrochemical ones as well as the electrolyte specifications and, of course, the composition of the metal itself and its surface conditions. Tuning the operating process parameters it is possible to obtain TiO₂ films that differ in terms of thickness, ranging from thin colored films up to complex micrometric thick ones; morphologies, from smooth to nanotubolar surfaces; oxide structures — from amorphous to anatase and rutile; and compositions. A precise and robust control of the anodizing process is of fundamental importance in tailoring properties of TiO₂ surfaces for biomedical applications.

Tribocorrosion performance of medical grade AISI 316L stainless steel with and without surface modification has been studied during exposure to an electrolyte. Some of the samples investigated were surface modified by plasma nitriding (at both 400 and 550 °C), and others by a special arc physical vapor deposition to secure a thin layer of a diamond-like carbon (DLC) coating on the surface of the samples. XRD and SEM were used to characterize the homogeneity and microstructure of all samples. Potentiodynamic polarization measurement and tribocorrosion tests were performed multiple times on all groups of samples. It was established that surface treated SS 316L exhibited totally different passive behaviors, which consequently lead different tribocorrosion performance in the electrolyte. It was also established that the DLC coating performed as a solid lubricant in the ball-on-plate tests, and the resulting wear track after the tribocorrosion tests was almost negligible. On the other hand, the untreated and Nitriding 400 °C samples experienced wear accelerated corrosion due to their passive behavior. The results suggest that the DLC coated SS 316L have the best performance at the combined wear and corrosion environment, while the untreated and Nitriding 400 °C samples should be avoided to apply in biological tribocorrosion conditions.

Titanium nitride (TiN) thin films were deposited on austenitic AISI 316L stainless steel substrate using magnetron sputtering method. The influence of process parameters of the magnetron sputtered on the thickness of the deposited layer and the corrosion resistance were investigated using factorial experimental design. The parameters studied included deposition rate and deposition time. The layer thickness was characterized by scanning electron microscopy (SEM). The corrosion behaviour was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results indicated that the deposition rate and deposition time have an influence both on the deposited layer and in the corrosion resistance.

Titanium (Ti) and Ti alloys are widely used for the manufacture of dental implants and orthopedic prostheses due to suitable properties such as zero toxicity, good mechanical properties and corrosion resistance. The addition of niobium (Nb) to commercially pure Ti (cp-Ti) can results in elastic moduli lower than Ti. So in this work the elastic modulus of Ti-Nb alloys with 10% and 20%, in weight submitted to anodic oxidation (AO) has been investigated to verify how to obtain elastic modulus closer to bone. The AO has been realized using phosphoric acid as electrolyte applying a voltage of 250V/60s. Elastic modulus values were obtained using instrumented indentation technique. The results indicated that it was possible to obtain Ti-Nb alloys with lower elastic modulus values compared with cp-Ti.

Perovskite manganites have attracted considerable attention recently due to inhomogeneities in multi-functional properties, observed by various high resolution probes. We present an analysis of the essential role played by complex energy landscapes in the nanometer to micron-scale inhomogeneities observed in perovskite manganites using a model expressed in terms of symmetrized atomic-scale lattice distortion modes. We also discuss the origin for the stability of large metal and insulator domains in the absence of defects. We demonstrate that an intrinsic mechanism, which specifically involves longrange interactions between strain fields, the Peierls-Nabarro energy barrier, and complex energy landscapes with multiple metastable states is responsible for the inhomogeneities in perovskite manganites. This is in contrast to an extrinsic mechanism such as chemical randomness. We highlight experimental results which support our intrinsic, rather than extrinsic, mechanism.

AlGaN/GaN high electron mobility transistors are gaining commercial acceptance for use in high power and high frequency applications, but the degradation mechanisms that drive failure in the devices are not completely understood. Since some of these mechanisms are current or field driven, reliability studies must go beyond the typical Arrhenius accelerated life tests. In this chapter we summarize recent work on electric field or current driven degradation in devices with different gate metallization, device dimensions, electric field mitigation techniques (such as source field plates), and the effect of defects either already present or introduced by exposure to ionizing radiation. Some of the mechanisms now established include gate or Ohmic metal reaction, hot carrier trap generation, stress-induced crack generation and oxidation reactions involving the AlGaN layer.

Chalcogenide glasses (ChG) are the advanced material for the emerging nanoionic memory devices — conductive-bridging RAM (CBRAM). In order to understand the nature of the effects occurring within these devices under the influence of electron - beam radiation, we studied the interaction of blanked chalcogenide films and nanostructured films containing chalcogenide glass and Ag source. Using Raman spectroscopy, EDS and XRD we established the structural and composition effects occurring under radiation, which have strong compositional dependence, and connected them to the availability of lone-pair electrons in the systems, their participation in the bonding configurations, and the coupling of electron states in the band gap. These effects are used to interpret the electrical performance after radiation of CBRAM devices, which were characterized with their resistance states, threshold voltage and endurance.

In this letter, we present a quantitative analysis of different electric field intensity on interface atom diffusion in a Cu/Ta/Si stack at 650 °C annealing. It was found that the external electric field accelerated the Cu atom diffusion in the Ta layer. With the increment of electric field intensity, the effect of the electric field upon the atomic diffusion becomes more significant. The mechanism of accelerated effect is mainly attributed to the perturbation of the electric state of the defects in the interface and grain interior.

Cadmium sulfide (CdS) continues to hold an important position among the solar cell materials and optoelectronic materials. It is usually used as window layer in the CdS/CdTe thin film solar cell. Indium doping of CdS increases its conductivity, which results in a lower series resistance of the solar cell. Optimizing the optical parameters of this material is important in getting high performance solar cells and in the use of the material in optoelectronic devices. In this work, polycrystalline indium doped cadmium sulfide (CdS:In) thin films were produced by the spray pyrolysis (SP) technique on glass substrates. Transmittance of the films was measured at room temperature in the wavelength range 400–1100 nm and used to deduce the optical parameters such as the absorption coefficient, extinction coefficient, refractive index, real and imaginary parts of the dielectric constant. The refractive index dispersion was analyzed by the single oscillator model and the oscillator parameters were computed.

Tin oxide is a transparent conductive oxide with potential use in heterojunction thin film solar cells such as CdS/CdTe solar cell as a fore contact, and in optoelectronic devices. These applications require a deep understanding of the optical properties of the material and optimization of its optical parameters. Fluorine doping of the films increases their conductivity, which is important for high cell performance. In this work fluorine doped tin oxide (SnO₂:F) thin films were prepared by the spray pyrolysis (SP) technique on glass substrates. The films were found to be polycrystalline as seen in the scanning electron microscope (SEM) images. The transmittance spectra of the films were measured at room temperature and used to deduce the optical parameters such as the direct and indirect optical bandgap energies, Urbuch tail width, extinction coefficient, and refractive index. The dependence of these parameters on film thickness was investigated.

Thermoelectric alloys, which can generate electricity from waste heat were gathering attention recently. ABX type ternary alloy in which A and B were transition metals and X was group IVA non-metal elements was studied mainly because of its distinct thermoelectric performance at elevated temperatures. Calculation of transport properties which included Seebeck coefficient, electrical conductivity and thermal conductivity of ABX type thermoelectric alloys were carried out. The properties of n-type TiNiSn thermoelectric alloys were discussed in detail which included the effect of dopant Nb and Sb, and the second phase formation. The derived empirical equations of transport property were tabulated. The predicted peak value of dimensionless figure of merit (ZT) and primary phases were evaluated. The maximum value of ZT was estimated using Arrhenius relationships for TiNiSn alloys.

For medium temperature applications, magnesium silicide stannide and manganese silicide (HMS) are considered as the most promising thermoelectric materials. The scale-up of these materials was performed by gas phase atomization for powder production, followed by Spark Plasma Sintering process in a pre-industrial scale technological platform for thermoelectrics “PAMIRE” (Grenoble, France). Kilograms batches of thermoelectric powder were processed, leading to the production of a large quantity of homogenous 60 mm diameter silicide pellets.The development of high performance materials was obtained by a deep investigation on the relation between thermoelectric properties and material microstructure. During the synthesis process nano/micrometric precipitates were formed. TEM analysis and thermoelectric measurements were systematically correlated. The figure of merit of the produced material reaches ZT_max of 1.4 and 0.54 for n-type and p-type materials respectively.Moreover, promising assembly processes for thermoelectric modules were initiated. The performances of first silicide modules produced by CEA-LITEN thermoelectric lab were measured on a specific bench, in conditions representative of applications (temperature and heat flux).

Group (II) metal borides and silicides have been studied as high temperature thermoelectric materials because of their good thermal stabilities and high melting points. In the present study, an investigation was carried out on thermoelectric and thermodynamic properties of group (II) metal borides (CaB₆ and SrB₆) and silicides (Mg₂Si and CaSi) at high temperatures (up to 1050 K). Experimental data on thermoelectric properties (Seebeck coefficient, electrical conductivity, thermal conductivity and figure of merit) of the borides and silicides was collected and evaluated as a function of temperature. Thermodynamic properties such as Gibbs energy and activities of B and Si in the binary alloys and corresponding binary phase diagrams were evaluated. Phase equilibria and crystal structure of the alloys were determined from the available binary alloy data. Mg₂Si exhibited better thermoelectric figure of merit and has greater potential for power generation at high temperatures.

This paper employs atomic absorption spectroscopy (AAS), Fourier transform infrared spectroscopy (FTIR) and phytochemical screening methods for biochemical characterisation of the inorganic and organic constituents of the leaf of Morinda lucida. AAS results showed that this well-known medicinal-plant is high in iron (Fe = 5143.54 µg/g), low in cadmium (Cd = 2.9506 µg/g) and does not contain chromium (Cr). Also, Euclidean hit-list from the FT-IR instrument suggests Morinda lucida leaf-extract contains S-, N-, Br- and O- containing heteroatoms. The phytochemical analyses indicated presence of tannins, phlobatannins, saponins, flavonoids and terpenoids. These results bare prospects on suitability of leaf-extract from Morinda lucida for environmentally-friendly steel-rebar corrosion-protection in aggressive medium. Preliminary tests based on this showed that use of 0.083 wt% cement of Morinda lucida retarded steel-rebar total-corrosion and eventually reduced corrosion rate as admixture in duplicated 3.5% NaCl-immersed concretes, relative to control samples in the same medium.

Subcutaneous Venous Access Ports (SVAPs) are commonly used during long-term placement for administration of antineoplastic drugs used in chemotherapy. A significant number of complications that can lead to implantation failure have over the years been reported, i.e. thrombosis and infections. These complications subsequently also increases patient suffering and health care costs.The main aim of the present preliminary in-vitro study was to monitor the inner surface alterations/degradations of polyurethane SVAPs exposed to antineoplastic drugs over a prolonged period of time (6 cycles during 18 weeks).The changes in surface structure and topography were analyzed both before and after each exposure to the drugs. Moreover, the degree of blood cluttering of the catheters was evaluated by exposing the outer surface of the drug-exposed catheters to whole blood. The results clearly indicate an association between the observed surface alterations and an increased blood cluttering.

A requirement for materials used to build prosthesis in contact with blood is a good hemocompatibility. However, there is no standard method to measure it. The first interaction blood-material is the adsorption of plasma proteins which determines the adhesion and activation of platelets which in turn derives in blood clotting. This sequence shows that adhesion and activation of platelets are the key steps in the interaction blood-material. In the present report the adhesion of platelets on titanium dioxide coatings produced by anodic oxidation is evaluated in vitro (direct counting). Coatings were produced in a range of applied voltages and different heat treatments. The results show a direct relationship between roughness platelets adhesion.

In the present research the adhesion of thin anodic coatings of TiO₂ (40 nm to 140 nm) is evaluated. Coatings were produced by anodic oxidation of Ti-6Al-4V, using H₂SO₄ as electrolyte at different voltages (20 V to 70 V), employing heat treatments of 1 h at 500 ℃ and 600 ℃.The adhesion of coatings was evaluated by scratch test with load rates of 2 N/mm and 4 N/mm and up to 10 N and 20 N of maximum load.The adhesion was dependent on the increasing load rates. At larger rate a brittle behavior was found and the critical load decreased with heat treatment temperature. For non-heat treated coatings, the critical load of adherence increased with coating thickness.

We report on the slurry erosion and cavitation behavior of a zirconium based bulk metallic glass (BMG), Zr₄₄Ti₁₁Cu₁₀Ni₁₀Be₂₅. Slurry erosion and cavitation tests were carried out using a non-circulating type test rig at different impingement angles. For comparative analysis, commonly used hydroturbine steel, CA6NM (13Cr4Ni), was also evaluated under similar test conditions. For low impingement angles, BMG demonstrated nearly 3 times higher erosion resistance compared to CA6NM. However, under normal impingement condition, BMG showed marginally better erosion performance. The cavitation resistance for BMG was four times higher compared to hydroturbine steel. The unusually high erosion resistance for BMG is attributed to its uniform amorphous structure with no grain boundaries, higher hardness, and ability to accommodate strain through localized shear bands.

The atomic structures of metallic glasses (MGs) are very sensitive to the cooling rates. Most molecular dynamics (MD) simulations suffer from the ultrahigh cooling rates on the order of 1010–13 K/s, where the as-prepared models are hardly given enough time to relax. In this work, an extended sub-T _g annealing up to 1.8 µs was applied to a Cu_64.5Zr_35.5 MG in order to reduce the effect of the high cooling rate used in MD simulations. The effective cooling rate after the sub-T _g annealing is derived to be 2×108 K/s, which is about two orders of magnitude lower than the cooling rates used in conventional MD simulations. The icosahedral short-range order and the Bergman-type medium range order (BMRO) are significantly enhanced after the annealing. The interpenetrating, face-, edge- and vertex-sharing schemes of connections among icosahedra are found to be enhanced after annealing. The network formed by the interpenetrated ICO centers clearly shows a transition from string-like to star-like in morphology. The diffusing atoms are found to be outside icosahedral SRO and BMRO for most of the simulation time. Our result supports the scenario that there are both liquid- and solid-like regions in MGs. The solid-like regions form the backbone while the liquid-like regions provide diffusion channels of the glassy structure.

In bulk polycrystalline materials, the first nucleation event of a martensite plate within a single grain may induce transformation in one or more neighboring grains, resulting in a cluster of partially transformed grains: ‘the spread event’. The collection of these single spread events can be defined as the ‘spread’ or ‘martensite spread’. First, in this paper, martensite spreads are analyzed to estimate the mean number of partially transformed grains in a single spread event. Secondly, taking the quantitative knowledge gained from this analysis as a starting point, a computer simulation of the martensite spread is proposed. This computer simulation is carried out in a 3-d network of space-filling grains represented as Kelvin polyhedra and is based on a stochastic approach. The experimental and simulation results are presented, compared and discussed. We conclude that the stochastic computer simulation of martensite spread could successfully describe important quantitative aspects of martensite spread.

We consider the choices and subsequent costs associated with ensemble averaging and extrapolating experimental measurements in the context of optimizing material properties using Optimal Learning (OL). We demonstrate how these two general techniques lead to a trade-off between measurement error and experimental costs, and incorporate this trade-off in the OL framework. As a first contextual example, we study the effect of ensemble size in determining the most accessible regions of an RNA molecule. A second example considers the impact of the number and frequency of initial measurements used to extrapolate a measure of nanoemulsion stability. In both cases, we use OL simulations to determine the optimal choice of these characterization parameters by minimizing an associated total experimental cost.

Composite materials due to their high stiffness to mass ratio as well as their anisotropic properties are the material of choice for many different weight critical structures such as wind turbine blades. Wind turbine blades have been modeled as composite cantilever box-beams for optimization purposes. The use of Genetic Algorithms (GA) has become a fairly common practice for optimization of composite laminates, where the objective is to find a laminate stacking sequence that optimizes the composite for a given condition. The purpose of this work is to study further adaptations to the GA search technique for use in the composite laminate stacking sequence optimization problem. In this work an Adaptive Genetic Algorithm (AGA) is studied for the stacking sequence optimization of a composite box-beam.

We reports the effect of substitution of Nb on the physical properties of Zr3Al1-xNbx using the FP-LAPW method based on the density functional theory (DFT) for structural, electronic, and mechanical properties. In order to understand the relative stability between L12 and DOa structures by the gradual substitution of Nb in Zr3Al, we have performed total-energy calculations for Zr3Al0.75Nb0.25, Zr3Al0.5Nb0.5, and Zr3Al0.25Nb0.75 in both L12 and DOa structures at different volumes. The first-principles calculations clearly show that the cubic symmetry, which favors greater ductility, is retained by the alloy up to the composition Zr3Al0.5Nb0.5 and hence may be of potential use for structural applications. The transition from cubic to orthorhombic structure is found to be in good agreement with experimental observation. The cohesive energy, equilibrium lattice constants, and bulk modulus, including its pressure derivative as a function of Nb substitution, are also calculated and compared with the available experimental values.

In the present work, the effect of uniaxial strain on oxidation behavior of nanoscale 3C-SiC has been studied by a reactive force field molecular dynamics (ReaxFF MD) simulation using the Si/C/H/O parameters previously described in [J. Phys. Chem. C 116 (2012) 16111–16121]. The strain values of 0.1 (uniaxial tensile) and -0.1 (uniaxial compressive) were applied during oxidation of SiC at 1000 K. Comparing with the unstrained structure, it shows that both of the tensile and compressive strain have enhanced the oxidation process, and the enhancement of tensile strain was more remarkable. By imposing strain to SiC slab, the generated amounts of CO and CO₂ have been slightly raised as well.

To obtain the relationship among the preparation process, structure and performance of porous titanium, theporouscharacteristics, such as geometrical shape, aperture size and pores distribution, which influence the mechanical properties of the porous titanium were simulated by COMSOL Multiphysics software. Based on the analysis of cross-section of porous products, a two-dimensional model can be used to study the deformation mechanism and stress distribution of porous titanium material. The results indicate that the porosity, distribution shape and size of the pore have different effects on the porous materialelastic modulus.

To prevent rupture phenomenon of the side dam (SD) in twin roll strip casting progress, the heat insulation layer (HIL) with low coefficient of thermal conductivity (CTC) was installed on the outer surface of SD. The influence of thickness and CTC of the HIL, CTC and preheating temperature of SD was analyzed by ANSYS. The results show that the thermal stress of SD without HIL acutely varies at the initial stage of casting. The curves of thermal stress can make slow variation and the thermal stress can be drastically reduced by the HIL. The thermal stress of SD reduced with the decreased of the CTC of SD in the range of 13.8 to 25.1 W·m-1·K-1, following a cubic curve rule. The thermal stress was decrease with increasing the CTC of side dam, following the rules of parabolic and cubic curve.

By making use of the heat of converter fume, a way to preheating the top-blowing oxygen has been proposed and researched. The three-dimensional model has been developed to analyze the mixing process of molten bath in converter with preheating oxygen. The volume of Fluid (VOF) method was employed to model three-phases including oxygen, molten steel, and liquid slag to simulate the behaviors of molten bath. The results show that as temperature of oxygen is raised from 300 K to 1200 K, the impacting depth, impacting diameter and velocity of molten bath first Increase obviously, and then decrease. The research results revealed a way of the heat of fume utilization, and the optimized preheating temperature of oxygen was obtained.

In this paper, electrochemical test-data were obtained from 0.5 M H₂SO₄-immersed steel-reinforced concrete admixed with different Rhizophora mangle L bark-extract concentrations and subjected to modelling analyses for studying corrosion-inhibition effectiveness. For this, macrocell current from zero-resistance ammeter and corrosion-rate from linear-polarization resistance instruments were respectively subjected to total-corrosion modelling as per ASTM G109–99a and statistical-distribution modelling as per ASTM G16–95 R04. Further analyses of these modelled test-results showed that the corrosion-rate correlated excellently (R = 95.04%, Nash-Sutcliffe efficiency = 90.33%, p-value = 0.037) with function of the bark-extract concentration and the total-corrosion from the steel-reinforced concrete samples. In agreements, both experimental and correlation fitting models identified 0.167% Rhizophora mangle L barkextract with good corrosion-inhibition efficiency, η = 73.30% (experimental) or η = 60.81% (correlation prediction). These bare implications on macrocell technique usage for complimenting identification of admixture concentration for effective corrosion-inhibition of concrete steel-rebar in the microbial/industrial simulating-environment studied.

Kinetic models of elements oxidation during vanadium extraction from hot metal by converter were established according to the theory of the metallurgical thermodynamics and reaction engineering. The results showed that silicon and titanium in hot metal were oxidized rapidly during the initial blowing stage (0 to 2min), and then vanadium began to be quickly oxidized after blowing 2 min. With temperature increasing, the oxidation rate of vanadium and carbon was transferred and carbon began to be oxidized quickly after 4.5 min blowing. In addition, the oxidation of manganese and chromium happened throughout the blowing process. It was found that the calculated values according to the kinetic models were well consistent with the practical data.

A computation fluid dynamics—simultaneous reaction model (CFD-SRM) coupled model has been proposed to describe the desulfurization behavior in gas-stirred ladles. For the desulfurization thermodynamics, different models were investigated to determine sulfide capacity and oxygen activity, and for the desulfurization kinetics, the effects of bubbly plume flow as well as oxygen absorption and oxidation reactions in slag eyes were considered. The equilibrium of (Al2O3)-(FeO)-(SiO2)-(MnO)-[S]-[O] shows more reasonability for determining the interfacial oxygen activity, and the Young’s model with the thermodynamic coefficient of 1.5 is the best for determining the slag sulfide capacity. As the kinetics coefficient is 0.8, the predicted sulfur content changing with refining time agrees well with the measured, and the oxygen absorption and oxidation reactions in slag eyes have an important effect on desulfurization.

The electroslag remelting (ESR) process has been used widely to produce large ingots of high quality based on the controlled solidification and chemical refining that can be achieved. The vibrating electrode method was used in the ESR process in this paper, which can improve the quality of solidification and reduce the energy consumption. A transient three-dimensional (3D) coupled mathematical model was developed to simulate the electromagnetic phenomenon, fluid flow as well as pool shape in the ESR process with vibrating electrode. The finite element volume method is developed to solve the electromagnetic field using mechanical APDL software. Moreover, the electromagnetic force and Joule heating are interpolated as the source term of the momentum and energy equations. The flow field, temperature profiles and pool shapes are demonstrated by the finite volume model of FLUENT software. The volume of fluid (VOF) approach is implemented for the two-phase flow. The solidification of metal is simulated by an enthalpy-porosity formulation. The multi-physical fields have been investigated and compared between the traditional electrode and the vibrating electrode in the ESR process. The results show that the behavior of metal droplets with traditional electrode is scattered randomly. However, the behavior of metal droplets with vibrating electrode is periodic. The maximum temperature of slag layer with vibrating electrode is higher than that with traditional electrode, which can increase the melting rate as to the enhanced heat transfer in the vicinity of the electrode tip. The parameters study show that when the amplitude and frequency of vibrating electrode increases, the cycle of behavior of metal droplets decreases significantly.

A two-dimensional cellular automaton model is adopted to simulate the ferrite (α)-austenite (γ) transformation in low-carbon steels. The preferential nucleation sites of austenite, the driving force of phase transformation, carbon redistribution at α/γ interfaces, and carbon diffusion in both the α and γ phases are considered. The model is applied to simulate the phase transformation and carbon diffusion during heating at 815°C, and subsequent cooling at 5°C/s to room temperature and tempering at 300°C-500°C. The process of heating at 600°C after cooling from 815°C, but prior to cooling to room temperature, is also simulated to compare to the tempering process. The results show that during the isothermal heating at 815°C, the carbon distribution becomes uniform gradually in both the α and γ phases. The subsequent cooling to room temperature at 5°C/s results in a non-uniform carbon distribution, while the uniformity increases with tempering temperature. During the 600°C heating, the carbon distribution is uniform within 1 min. The simulation results are used to understand the processing-microstructure-property relationships of an enameling steel.

The mechanism on the interaction among C, N and Ti₃O₅(100) surface in the process of Ti(C,N) formation has been investigated using the density functional theory (DFT). The results revealed that there are three stages in the reaction process: oxygen vacancy generation, competition of C and N adsorption onto the oxygen vacancy site, and the internal diffusion of O, C and N. In the first step, C is favorably adsorbed onto the three top O sites of the Ti₃O₅(100) surface to form CO, the oxygen vacancy could be generated after the CO dissociates from the surface. In the second step, C and N are competitively adsorbed onto the oxygen vacancy sites, the adsorption energy for N is larger than that for C. In the third step, internal diffusion of O, C and N takes place in the Ti₃O₅(100). The barrier for C to diffuse into the Ti₃O₅(100) is estimated to be 0.38eV, which is lower than that for N and O. The results suggest that internal diffusion of O in the Ti₃O₅(100) is controlling the formation of Ti(C,N).

We describe the study of thermodynamics of materials using replica-exchange Wang—Landau (REWL) sampling, a generic framework for massively parallel implementations of the Wang—Landau Monte Carlo method. To evaluate the performance and scalability of the method, we investigate the magnetic phase transition in body-centered cubic (bcc) iron using the classical Heisenberg model parametrized with first principles calculations. We demonstrate that our framework leads to a significant speedup without compromising the accuracy and precision and facilitates the study of much larger systems than is possible with its serial counterpart.

To improve extraction of vanadium from vanadium slag, a better understanding of the structure and physicochemical properties relation of FeO-SiO₂-V₂O₃ system is very important. In this study, the structural and transport properties of the FeO-SiO₂-V₂O₃ system were investigated by means of molecular dynamics simulation with the molar fraction of V₂O₃ varying from 0 to 20% at a fixed FeO/SiO₂ ratio of 1.5. It was found that with the addition of V₂O₃, Si remains tetrahedral coordination while the coordination number of V increased gradually from 4.56 to 5.06. The fraction of Q4 (tetrahedron with 4 bridging oxygen (BO)) decrease while non-bridging oxygen (NBO) increase suggesting that depolymerization of the network, and the variation of the self-diffusion coefficients of different ions also agree with the structural findings. Thus, V₂O₃ is regarded a basic-like oxide which acts as network modifier and then decreases the viscosity of the FeO-SiO₂-V₂O₃ system.

The magnetic properties of non-oriented silicon steel are closely associated the precipitates in steel. To study and analyze the effect of the size, morphology and distribution of sub-micron grade precipitates on the magnetic properties of silicon steel, some experiments has been carried out by using transmission electron microscope (TEM) technique. In addition, the precipitation temperature of precipitates is calculated by using the thermodynamic software Thermo-calc. The results shown that, most of the precipitates are spherical particles, with sizes ranging from 10 nm to 500 nm. Manganese sulfide precipitation temperature is about 1250 °C, the precipitates of different sizes corresponding to different precipitate types, the size of single copper sulfide precipitation is smaller than compound precipitates, The size of copper sulfide and manganese sulfide compound precipitates increases with the content of manganese sulfides, the size of separately precipitated manganese sulfides are larger.

The activities of components in Cu-Ni alloy were predicted based on the molecular interaction volume model (MIVM). The required binary parameters B _ij and B _ji were determined by using the Newton—Raphson methodology with the aid of the experimental data of infinite dilution activity coefficients γ_i∞, γ_j∞. The predicted values of the activities match well with the experimental data, which show that the predicting effect of this method is reliable due to the MIVM has a good and clear physical basis. The separation coefficients of Cu-Ni alloy were far larger than 1. The vapor-liquid phase equilibrium of Cu-Ni alloy was also predicted by using the activity coefficients, which indicates that Cu and Ni can be concentrated in vapor phase and liquid phase respectively by vacuum distillation. This study extends previous investigations and provides an effective and convenient model on which to base separation simulations for Cu-Ni alloy by vacuum distillation.

Gasification is a well-known reaction owing to its relevance to generation of sustainable energy from biomass. The present paper attempts to experimentally investigate the kinetics of coal char (CC) and biomass char (BC) gasification using carbon dioxide (CO₂) in a controlled environment using Thermo Gravimetric Analyzer (TGA) at different temperature. The random pore model (RPM) and a modified random pore model (MRPM) proposed in this paper were used to investigate gasification kinetics of CC and BC. It was clarified that gasification reactivity of BC is superior to that of CC and gasification reactivity of both chars were improved with increase of temperature, while the influence of temperature on biomass char gasification reactivity is more obvious. Kinetic analysis showed that, since the CC particles were approximately spherical in the shape, the RPM model and the MRPM model could both be used to characterize its gasification process, but flake-like BC gasification process could only be explained by the MRPM. The activation energy for CC and BC using the MRPM are 194.3kJ/mol and 123.3kJ/mol, respectively.

Biomass gasification is a well-known owing to its relevance to generation of sustainable energy to save the traditional coal fossil fuel consumption. The influence of gasification temperature (850–1050°C) on biomass char gasification were performed in Program reduction furnace (PRF) and in order to keep the reaction in the chemically controlled regime, the gasification temperature 900°C was selected to conduct the rest of experiments. Based on PRF studies, the catalytic effect of Fe₂O₃, MnO₂ and MgO on the gasification reaction of biomass char (BC) was studied in TGA and the results showed considerable improvement in carbon conversion: Fe₂O₃-char > MnO₂-char > MgO-char > raw biomass char. Therefore, Fe₂O₃ (with loadings of 1–7 wt%) was selected as the superior catalyst for further gasification studies; the highest reactivity was devoted to 5 wt% Fe₂O₃ loaded char. The data acquired for gasification rate of catalyzed char was fitted with several kinetic models, among which, random pore model was adopted as the best model. From the Arrhenius curve fitting results, the activation energy of 5 wt% Fe₂O₃ loaded char was obtained 249.8 kJ/mol which was 81.1 kJ/mol lower than that of un-catalyzed char.

Kinetics of biomass char (BC)/coal char (CC) blends at five mass ratios in 30%O2-70% N2 atmosphere were studied using the isothermal thermo-gravimetric method. The combustion reaction process was simulated by using random pore model (RPM), unreacted core model (URCM) and volumetric model (VM). The results show that the combustion property of the blended char was in relationship with the biomass char blending ratio and the isothermal combustion temperature. When increasing the biomass char (BC) share and the combustion temperature, the combustion rate can be increased apparently with more less time. It can also be described by the kinetics calculation that the RPM model is the optimized model to represent the combustion process. For each biomass char (BC)/coal char (CC) ratio in the mixture, the activation energy and pre-exponential factor were determined using the Arrhenius equation.

We investigate solid-like clusters in supercooled liquid Fe by molecular dynamics (MD) simulations. Average bond orientational order (ABOO) parameters and Voronoi polyhedron (VP) method were used to identify the local structure and local volume of each atom. We analyzed the size distributions, local environment and bond-length of solid-like clusters. There is a linear relation between the logarithm of number of incipient solid-like clusters (ISLC) and their sizes. Moreover, we tracked the born, growth and coalescence processes of these clusters and discuss their behaviors in detail.

We investigated the crystallization in three supercooled liquids of three kinds of representative elemental metals, i.e. BCC-V, HCP-Zn and FCC-Al, by molecular dynamics simulations. We used bond orientational order parameters and Voronoi polyhedron methods to analyze the crystalline structure evolution during the crystallization. We further compared the crystalline structure evolutions of three kinds of metals. All of these liquid systems first transform to metastable phases, and then gradually transform to the stable phase. This is in accordance with the Ostwald step rule.

A computational tool together with a thermodynamic database has been used to study the manufacturing of Portland cement clinker. In this paper is examined the potential of thermodynamic calculation of phase equilibrium to contribute to understanding the cement chemistry. Calculations were performed on a relevant part of the quaternary system CaO-SiO2-Al2O3-Fe2O3 which is the basis of the high temperature chemistry in the rotary kiln. High temperature equilibria calculations were performed in order to study the process taking place in the kiln in a temperature range consistent with the process (700–1600°C). Phases coexisting were determined, their distribution and stability ranges. Phase transformation on cooling was study using a non-equilibrium model to predict the final phase distribution. The results were compared with Bogue calculations. We discuss the scope and limitations of the database and the method used in this research.

The effect of protecting blast furnace (BF) can be achieved by smelting the iron ores containing titanium. The formation of Ti(C,N) in the slag causes bubbles resulted in the difficult separation of slag and iron. The concentration of titanium in hot metal with slag-iron reaction reaching equilibrium and the solubility of titanium in hot metal are calculated by FactSage software. The results show that the concentration of titanium in hot metal with slag-iron reaction reaching equilibrium is equal to 1.042% and the solubility of titanium in hot metal is 0.5588. The most effective factor of decreasing TiO2 activity is binary basicity (R2=CaO/SiO2), followed by temperature , MgO content, Al2O3 content.

The rheology characteristics of blast furnace (BF) slag with solid-liquid coexistence system were simulated by the method of Dissipative Particle Dynamics (DPD). In this approach, solvent particles, such as Ca, Si, Ti, O were still represented as DPD particles to retaining the time and length scale advantages offered by the DPD approach, and the solute particles TiC were represented by particles with appropriate mass and size by coarse-graining technique. This work focused on the equilibrium dynamics and the steady-state shear rheological behaviors for a range of volume fractions of the solid particles-TiC. The results showed that the theological properties of BF slag could be well examined quantitatively in this approach.

Experiments were carried out by adding NaF as catalyst in a Ar atmosphere to study the isothermal reduction kinetics of vanadium titano-magnetite carbon composite pellets under high temperature in the range from1473 to 1673K. By analyzing reduction mechanism, it was found that the rate controlling step was gas diffusion, and the activation energy was 178.39kJ•mol-1 without none catalysts. Adding NaF of 3% to vanadium titano-magnetite carbon composite pellets can decrease the apparent activation energy of reduction, and the decrease extent was 15.79kJ•mol-1. In addition, temperature is an important factor influencing on reaction rate.

To obtained high titanium slag and so as to improve the comprehensive value of sea sand ore, we used smelting reduction technology and all vanadium-titanium magnetite iron ore in the experiments. Under the condition of different temperatures and raw materials, the reduction rate constant was calculated between 0.01–0.04 g(Fe)/(cm2•min•kg(slag)), and the activation energy was calculated at 792 kJ/mol. In the process of experiments, the flow ability of slag was fine and the foaming slag was in control. The result of the detection showed that there was no TiC in the slag.

A continuum yield surface model is developed to describe the evolving anisotropic response of polycrystalline HCP metals over a wide range of strains, strain rates, and temperatures. The model is intended for large-scale parallel finite element codes for both implicit quasistatic and explicit dynamic simulations. Although the yield function is sufficiently general to capture the range of behaviors exhibited by a variety of HCP materials, the parameterization and evaluation is conducted primarily on Magnesium alloy AZ31. The model exhibits sufficient flexibility to capture the anisotropic response of AZ31 under various loading conditions with lower computational cost and complexity than high rate single crystal models. Consequently, it is foreseeable that by fitting the function to high rate polycrystal plasticity results, it may be used as an intermediary to extend crystal mechanics to engineering-scale applications.

The effect of microstructural anisotropy on the mechanical response of a heavily rolled 7010 – T7651 Al alloy has been investigated. A comprehensive set of quasi-static and dynamic (shockloading) experiments were conducted on specimens with their loading axis along the rolling (RD) and through-the-thickness (TT) directions. Deformed specimens were characterized via optical and electron backscatter diffraction techniques. The results show that specimens tested along the TT direction exhibit a higher elastic limit and moduli; whereas specimens tested along the RD direction exhibit a higher ductility and fracture stress. For the case of shock-loaded specimens, it was found that void nucleation was dependent on the grain boundary orientation with respect to the applied load, whereas angle misorientation and Taylor factor differences of adjacent grains did not contribute significantly to the damage development.

The creep deformation, damage, and life of creep susceptible components are a function of temperature, stress and strain rate. In this study the Kachanov-Rabotnov (KR) creep damage constitutive model and a recently developed Sinh creep damage constitutive model are compared in terms of accuracy, considerations/assumptions, constants evaluation techniques, flexibility in use, and limitations for 304 Stainless Steel (STS). Twenty tests performed at four different configurations of stress and temperature (five repeats for each) are collected from literature and used. It is found that the novel Sin-hyperbolic model exhibits lower constant dependency, is easier to apply, and more accurately models the creep deformations and damage evolution of 304 STS. The Sin-hyperbolic model produces a continuous damage (from zero to unity) by normalizing the experimental data while the KR model produces critical damage values well below unity. It is found that overall the new Sin-hyperbolic model offers more flexibility and prediction accuracy.

This paper focuses on measuring local strain at micro-crack initiation in fully ferritic cast iron alloys, using micro-scale strain mapping. Strain mapping was achieved using in-situ tensile test under optical microscope combined with digital image correlation (DIC). A previously developed pit etching procedure was used to create microscale random speckle patterns in the microstructure of the tensile specimens. Real-time microscope images were recorded during tensile deformation and analyzed by using DIC technique. Local strain values were measured around early formed micro-cracks during deformation. Results showed a heterogeneous deformation in microscale level. The micro-cracks were initiated at well-defined local strain levels but with large variations in the global strain level. Crack initiation was strongly associated with the graphite particles and their morphology.

Aluminum alloys are increasingly being used in a broad spectrum of load-bearing applications such as light rail and marine crafts. Post-fire evaluation of structural integrity and assessment of the need for structural member replacement requires an understanding of the residual (post-fire) mechanical behavior. In this work, models are presented to predict the residual (post-fire) constitutive behavior, including yield strength and strain hardening, at ambient conditions following fire exposure. This model consists of a series of sub-models for (i) microstructural evolution, (ii) residual yield strength, and (iii) residual strain hardening behavior. Kinetics-based (time-temperature dependent) models were implemented to predict microstructural evolution during fire, i.e., recovery and recrystallization for 5xxx-series Al alloys.. The residual yield strength is predicted using individual strengthening contributions and which are function of the microstructural material state. The residual strain hardening behavior is predicted using the Kocks-Mecking-Estrin law modified to account for the additional dislocation storage and dynamic recovery from subgrains. The constitutive model for residual mechanical behavior was bench-marked against AA5083-H116 specimens exposed to conditions resembling those in fire. The residual yield strength and strain hardening models show good agreement with experimental data.

The constitutive behavior of as-quenched Al-5%Cu-0.4%Mn, one of high strength cast aluminum alloys, was investigated by using hot tensile tests. The tensile tests were designed and conducted in the temperature range from 25°C to 500°C and the strain rate from 0.0005s-1 to 0.05s-1. The Arrhenius constitutive model was developed under small strain (>0.018) based on thermal activation to present the relationship between flow stress and deformation conditions (temperature and strain rate at tension state). The calculated flow stresses are in good agreement with experimental results with a deviation of less than 3%. The constitutive model can be used to model quenching distortion and residual stresses of Al-5%Cu-0.4%Mn alloy parts at high temperature and tension state. Compared with existing research results, the stress-strain curves at tension state are inconsistent with compression state for as-quenched Al-5%Cu-0.4%Mn alloys. Furthermore, some phenomena in dynamic tensile tests with temperature range from 25°C to 500°C has been discussed, which help on comprehensive understanding about interaction between microstructure and mechanical properties of aluminum alloys.

An accurate description of the mechanical response of metals subjected to high strain rate dynamic loading is important as analyses on high speed metal cutting and automobile crash. In this paper, a physical based constitutive model on the thermal activation mechanism and dislocation dynamics was proposed to present such plastic deformation of Fe-Cr-Ni stainless steel. The dynamic compression loading experiments were carried out by using the Split Hopkinson Pressure Bar (SHPB) at different temperature and strain rate. Material parameters in the constitutive model were determined with a nonlinear optimization algorithm. The constitutive model was implemented in ABAQUS/VUMAT to simulate the adiabatic shear band formation of the “hat” shaped specimen. The comparison between numerical and experiment results validates that the constitutive model proposed is capable to predict the mechanical response of Fe-Cr-Ni stainless steel under dynamic loading.

As-rolled and annealed microstructures of Zr-free and Zr-containing (2 and 10 wt. % Zr) αTi alloys have been evaluated by optical microscopy and analytical transmission electron microscopy. In the as-rolled samples, grain refinement by the Zr addition is accomplished, and 0.2% proof stress of 833 MPa in the 10Zr alloy is obtained. The mechanical properties are enhanced as the Zr content increases. When annealing is applied to the as-rolled samples at 750 °C, then rapid grain growth of recrystallized grains occurs in the Zr-free alloy. However, it is found that the grain growth is sufficiently suppressed by the Zr addition due to a solute drag effect, and this is obvious when the Zr content increases. The grain refinement by the Zr addition leads to high strength in the Zr-containing alloys as similar to the as-rolled samples following the Hall-Petch rule.

Recent results show that fatigue crack initiation in very high cycle fatigue regime can occur at a non-defect origin in the matrix. The mechanism is not well understood. This paper provides a study on the influence of cyclic loading on the damage behavior at grain and twin boundaries in Alloy 690 material. The results show that the strains in the fatigue-tested specimen were highly localized, which were mainly caused by the dislocation accumulation in the grains with high Schmid factors during each small cyclic loading. This has led to the formation of local fine grain area consisting of numbers of new twins. The study also shows that the impingement between slip bands and grain or twin boundary is one of the main fatigue damage mechanisms. The results in this paper indicate that the role of a twin or grain boundary to block dislocation slip transmission depends on crystal orientation, Schmid factor and boundary orientations.

Vehicle lightweighting via the use of aluminum alloys is considered as one of the most important methods to meet stringent fuel-efficiency regulations and reduce CO₂ emissions. Design of aluminum components requires strain-controlled low-cycle fatigue (LCF) behavior. This study was aimed at evaluating cyclic deformation characteristics and LCF life of an Al-7Si-1Cu-0.5Mg (wt.%) as a base alloy and the alloys with different additions of V, Zr and Ti elements in a T6 heat-treated condition. The base alloy contained typical phases of aluminum matrix, eutectic silicon, Mg-rich and Fe-rich particles. A small amount of Zr and V additions led to a complex microstructure. Increasing the amount of Zr, V and Ti resulted in the presence of a ductile type of Zr-V-Ti-rich particles. This effectively improved the ductility, ultimate tensile strength and fatigue life of this alloy, despite a slightly lower yield strength. Characteristic fatigue striations were observed to be presented not only in the aluminum matrix, but also in the Zr-V-Ti-rich particles.

Reactor internal components in the nuclear industry are typically made of stainless steels. These components are exposed to radiation being situated next to the core. With nuclear power plants extending the life of the reactor vessel internals, the effects of irradiation on the fatigue behavior of core internals needs to be fully investigated. In this study, the ultimate strength and hardness are approximated based on the radiation fluence for stainless steels. Bäumel-Seeger Universal Materials law and Roessle-Fatemi Hardness method are then used to predict fatigue lives of irradiated stainless steels based on ultimate strength and hardness. The predictions are compared with experimental results from literature for Stainless Steels 304, 304L and 316. Predicted fatigue lives only based on dose in displacements per atom are in good agreement with experimentally observed fatigue lives.

In-situ stress-strain testing under corrosive environment, such as corrosive gasses (e.g. CO₂) and highly saline water, is a challenge in testing corrosion fatigue of materials, e.g. for geothermal application or CCS (carbon capture and storage). The first corrosion chamber system was designed for performance at ambient pressure up to 100 °C. The second allows for corrosion fatigue testing at high pressure up to 200 bar and 400 °C. The highly flexible corrosion chambers allow for fast changing and easy alignment of test samples, visual monitoring, CAD-camera monitoring electrochemical measurements, O₂-partial pressure or gas partial pressure measurement. Novelty is the fixing of the corrosion chamber directly onto the specimen, that guarantees best fitting and enables the test system to be modified easily suiting a variety of fatigue test machines. All parts of the test system are conforming to the technical rules.

Ductile fracture and extremely low cycle fatigue (ELCF) [1] are two common failure modes in aircraft engines and turbomachinery designs [2]; however, the linkage between these two failure modes under multi-axial loading conditions has never been systematically studied. Inconel 718 (IN718) is one type of high temperature alloys widely used in turbomachines. Specially designed specimens and tests were used to achieve desired multi-axial loading conditions. Two groups of tests were conducted: (a) round bar specimens with different notches; (b) plane strain specimens. Similar types of tests were conducted for IN718 under both types of failure modes (ductile fracture and ELCF). It is found that the ductile fracture of IN718 under multi-axial loading conditions is strongly dependent on stress triaxiality, but weakly dependent on the Lode angle parameter [3]. A 3D fracture locus was calibrated using modified MohrCoulomb (MMC) criterion proposed by Bai and Wierzbicki [4]. It is found that the same phenomenon of stress state dependency exists in the ELCF, which need to be addressed. The mechanism linkage between these two failure modes was explored.

One of the most significant problems associated with the implementation of high strength steels for offshore applications lies with the guarantee of welded joint reliability. An aspect of particular interest is the through thickness variation of heat affected zone toughness of thick section (above 60 mm) high strength steels. An experimental study combining microstructural investigations with a new adjusted sub-sized CTOD test was conducted in order to assess the fracture toughness in the heat affected zone (HAZ) of welds on high strength steels. The emphasis was placed on the coarse grain HAZ. The effects of variations in alloying and inclusion content on the microstructure and toughness properties have been studied. Results show that fracture toughness decreases in the mid-section of thick plates, which could be a result of non-uniform microstructure with local centerline segregation bands, larger grain sizes and inclusions, which act as crack initiation sites.

One of the key defects in composite materials is the large variability in mechanical properties. To capture the variability of strength in FRPs, random microstructures have to be analyzed. Developing a realistic model for generation of random microstructures required first imaging a carbon reinforced epoxy and then quantifying prominent microstructural features. Microstructures were synthetically generated including experimentally observed microstructural features such as elliptical fibers, alignment fibers, voids, and resin seams. Material periodicity of microstructures was considered to facilitate the application of displacement periodic boundary condition for later finite element analysis.

A 3D NURBS-based interface-enriched generalized FEM (NIGFEM) is developed to analyze problems with complex, discontinuous gradient fields commonly observed in the structural analysis of heterogeneous materials, with emphasis on polymer matrix composites. In the proposed approach, the mesh generation process is significantly simplified by utilizing simple structured meshes that do not conform to the complex microstructure of the heterogeneous media. In the current study, we utilize the NIGFEM scheme to study the impact of microstructural statistics on the initiation and evolution of the damage in polymer matrix composites. For this purpose, we incorporate a three-parameter continuum damage model into our NIGFEM solver to capture the failure response of the matrix in a unidirectional composite layer. Finally, through an example, the results of a preliminary study of the correlation between some statistical measures of the microstructure and the damage behavior of the fiber-reinforced polymer matrix composites are presented.

Numerical simulations of component behavior and performance is critical to develop optimized and robust load-bearing components. The reliability of these simulations depend on the description of the components material behavior, which for e.g. cast and polymeric materials exhibit component specific local variations depending on geometry and manufacturing parameters. Here an extension of a previously presented strategy, the closed chain of simulations for cast components, to predict and incorporate local material data into Finite Element Method (FEM) simulations on multiple scales is shown. Manufacturing process simulation, solidification modelling, material characterization and representative volume elements (RVE) provides the basis for a microstructure-based FEM analysis of component behavior and a simulation of the mechanical behavior of the local microstructure in a critical region. It is discussed that the strategy is applicable not only to cast materials but also to injection molded polymeric materials, and enables a common integrated computational microstructure-based approach to optimized components.

The microstructural evolution of Ti(C,N)-Mo₂C-Ni cermets with/without Cu were investigated. The microstructures of them were core-rim structures, regardless of Cu contents. Cu existed in Ni binder phase. In the case of lower Ni content, the contiguity of the hard phase for the cermets with/without Cu is same. On the contrary, in the case of higher Ni content, the contiguity of the hard phase for the cermets with Cu is lower than that without Cu.

The decomposition of the solid solution KFe₃(SO₄)_2-x(CrO₄)_x(OH)₆ and its capacity to detain CrO₄2- under alkaline conditions were studied. A solution of Ca(OH)₂ was the media used. The incorporation of CrO₄2- in crystalline structure of jarosite, resulted in a solid solution with the following approximate formula: [K_0.86(H₃O)_0.14]Fe_2.67[(SO₄)_1.23(CrO₄)_0.77][(OH)_5.01(H₂O)_0.99]. The experimental data describe a reaction based in the model of decreasing core with chemical control. Decomposition curve shows an induction period, characterized by the formation of active centers where is initiated and established a reaction front, that is the beginning of the progressive conversion period, during which is formed a layer of inert products of Fe(OH)₃ and is characterized for the massive diffusion of K+, SO₄2- and CrO₄2- toward the solution. However, the mappings by SEM-EDS from a particle decomposed partially, shows that the SO₄2- is released preferentially, meanwhile, an important quantity of the CrO₄2- is adsorbed in the layer of Fe(OH)₃.

In this work, a kinetic analysis of the decomposition process of a solid solution of ammonium and sodium jarosite with arsenic incorporated into its structure in NaOH medium is presented. Atomic absorption spectroscopy (AAS), inductively coupled plasma optical emission spectroscopy (ICP-OES), elemental analysis and X-ray diffraction (XRD) were used for the characterization of the solid solution and the decomposition products. According to the results, the approximate stoichiometry of the jarosite synthesized is as follows: [(NH₄)_0.72Na_0.06(H₃O)_0.21]Fe_{3 2.52}(SO₄)_1.85(AsO₄)_0.15[(OH)_4.41(H₂O)_1.59].It was found that the alkaline decomposition reaction proceeds through an induction period (equation 1), followed by a progressive conversion period (equation 2). (1)<math display='block'> <munder> <mo>&#x2212;</mo> <mi>&#x03B8;</mi> </munder> <mo>=</mo><mfrac> <mrow> <msub> <mi>r</mi> <mn>0</mn> </msub> </mrow> <mrow> <msub> <mi>V</mi> <mi>m</mi> </msub> </mrow> </mfrac> <mo>&#x22C5;</mo><mn>9.7684</mn><mo>&#x00D7;</mo><msup> <mn>10</mn> <mrow> <mn>10</mn> </mrow> </msup> <mo>&#x22C5;</mo><msup> <mi>e</mi> <mrow> <mo>&#x2212;</mo><mn>65</mn><mo>,</mo><mn>030</mn><mo>/</mo><mi>R</mi><mi>T</mi> </mrow> </msup> <msup> <mrow><mo>[</mo> <mrow> <mi>O</mi><msup> <mi>H</mi> <mo>&#x2212;</mo> </msup> </mrow> <mo>]</mo></mrow> <mrow> <mn>.22</mn> </mrow> </msup> </math>$$\mathop - \limits_\theta = \frac{{{r_0}}}{{{V_m}}} \cdot 9.7684 \times {10^{10}} \cdot {e^{ - 65,030/RT}}{\left[ {O{H^ - }} \right]^{.22}} $$(2)<math display='block'> <mn>1</mn><mo>&#x2212;</mo><msup> <mrow><mo>(</mo> <mrow> <mn>1</mn><mo>&#x2212;</mo><mi>X</mi> </mrow> <mo>)</mo></mrow> <mrow> <mn>1</mn><mo>/</mo><mn>3</mn> </mrow> </msup> <mo>=</mo><mn>3.4395</mn><mo>&#x00D7;</mo><msup> <mn>10</mn> <mn>6</mn> </msup> <mo>&#x22C5;</mo><msup> <mi>e</mi> <mrow> <mo>&#x2212;</mo><mn>51</mn><mo>,</mo><mn>580</mn><mo>/</mo><mi>R</mi><mi>T</mi> </mrow> </msup> <msup> <mrow><mo>[</mo> <mrow> <mi>O</mi><msup> <mi>H</mi> <mo>&#x2212;</mo> </msup> </mrow> <mo>]</mo></mrow> <mrow> <mn>0.94</mn> </mrow> </msup> <mi>t</mi> </math> $$1 - {\left( {1 - X} \right)^{1/3}} = 3.4395 \times {10^6} \cdot {e^{ - 51,580/RT}}{\left[ {O{H^ - }} \right]^{0.94}}t $$

In this paper, the authors represent the mechanical properties of WC-FeAl composite fabricated with two sintering techniques. The WC-FeAl composite often is obtained through liquid-phase sintering process by conventional vacuum sintering technique. Contrary, the use of pulse current sintering techniques enables to density the WC-FeAl composite at a temperature lower than that of FeAl liquid phase formation. That difference of sintering temperature results in crucial difference of the microstructure of the composites. Fine WC grains and small FeAl phases are observed in the composite fabricated from the pulse current sintering technique, whereas some WC grain growth and huge FeAl phases are observed from the sample of vacuum sintering technique. As a result, superior mechanical properties such as Vickers hardness and bending strength are obtained from the samples of the pulse current sintering technique in the WC-FeAl system.

Halogen-free fire retardant (HF-FR) composites with good mechanical properties are important in the manufacturing sector and Polypropylene (PP) is one of the most widely used polymers in composite applications. However, PP is highly flammable and its flame retardancy is becoming more and more important. This paper reveals an environmentally friendly, cost effective technology to reduce flammability and improve physical properties of PP. The research involves the development of HF-FRPP with a polymeric fire retardant additive, based on ammonium polyphosphate (APP) labelled as AMP and a nano filler, exfoliated and intercalated within the polymer matrix contributing to enhanced mechanical properties useful in many technology platforms. The goals achieved in this research include determining optimal formulations of HF-FRPP, based on effective FR additive with a low dosage of cost effective nano-fillers that are able to transfer effectively into the manufacturing industry.

With the boom in of the use of plant extracts for synthesis of nanoparticles arises the need to identify plants species that have this potential. One of the challenges facing the synthesis of nanoparticles for green chemistry is to achieve stability of the nanoparticles obtained. The stability of produced nanoparticles can in some cases changes after a few days or can remain stable over long periods. In these work, the extract were characterized with FTIR analysis indicated the involvement of carboxyl (-C= O), hydroxyl (-OH) and amine (-NH) functional groups. The formation of AgNPs were characterized using UV-visible absorption spectroscopy gave surface plasmon resonance between 450 and 500 nm this reveals the reduction of silver ions (Ag+) to silver (Ag0) and scanning electron microscopy (SEM-EDS). The obtained particles were kept 4 months stability in aqueous solution, observing the absorbance characteristic plasmon by UV-visible spectroscopy for this time period.

These green methods are low cost, fast, efficient and generally lead to the formation of crystalline nanoparticles with a variety of shapes (spheres, rods, prisms, plates, needles, leafs or dendrites), with sizes between 1 and 100 nm. These features mainly depend on the process parameters, such as the nature of extract, concentrations of the reactants, pH, temperature, and time of reaction. This work shows obtaining bimetallic nanoparticles urchin-like using extract from Ricinus communis (Family Euphorbiaceae). In these work, the extract were characterized with FTIR analysis indicated the involvement of amine (-NH), hydroxyl (-OH) and carboxyl (-C= O) functional groups. The formation of nanoparticles were characterized using UV-visible absorption spectroscopy gave surface plasmon resonance between 425 and 445 nm this reveals the reduction of silver ions (Ag+) to silver (Ag0) and scanning electron microscopy (SEM-EDS) for the morphology. The nanoparticle obtained by this extract presents urchin-like formations with nanometer peaks.

Non-isothermal combustion experiments of different additive amount of biomass char (0,20,40,60,80,100 wt%) at heating rates of 5, 10 and 20 K/min were conducted by synthesized thermogravimetry analyzer(STA409PC) from room temperature to 900°C in air atmosphere. The changes of combustion characteristic parameters of pulverized coals in different conditions were analyzed. The results obtained from TG and DTG curves showed that the combustion process could be divided into three stages, and DTG curves of coal combustion moved to low temperature zones when the amount of biomass char increased which indicated that both ignition and burnout combustion temperature were lower. The burnout time tended to decrease and the combustion characteristic index increased obviously which mean that the combustion performance of pulverized coals with different additive amount of biomass char were improved.

The coarsening process of the decomposed phases was studied in the Cu-34wt.%Ni-4wt.%Cr and Cu-45wt.%Ni-10wt.%Cr alloys aged at 600, 700 and 800 °C for different times by transmission electron microscopy. The morphology of the coherent decomposed Ni-rich phase changed from cuboids to platelets aligned in the <100= Cu-rich matrix directions as aging progressed. The variation of mean equivalent radius of the coherent decomposed phases with aging time followed the modified LSW theory for thermally activated growth in ternary alloy systems. The linear variation of the density number of precipitates and matrix supersaturation with aging time, also confirmed that the coarsening process followed the modified LSW theory in both alloys. The size distributions of precipitates in the Cu-Ni-Cr alloys were broader and more symmetric than that predicted by the LSW theory. The coarsening rate was faster in the symmetrical Cu- 45wt.%Ni-10wt.%Cr alloy due to its higher volume fraction of precipitates.

High entropy alloys offer a new approach in alloy design by combining multiple elements around equiatomic proportions; relatively simple crystal structures may be obtained and promising properties have been reported. However, there is a major challenge to validate complex phase equilibria predictions for such multifold chemistries, and subsequently, to optimize composition within a selected alloy system. In the present case, high-throughput techniques were employed for the synthesis and characterization of thin films of varying composition around the equiatomic FeNiCoCuGa composition. Continuous thin films were deposited by modified molecular beam epitaxy (MBE) technology and annealed in a reducing atmosphere. Subsequently, the thin films were characterized by EDS, SEM and XRD. The results allow isothermal and isochemical sections of the quinary phase diagram to be drawn, revealing domains of three disordered crystalline phases, as well as mapping of their relative concentrations. General trends of the effect of the constituent elements on the phase concentrations and domain of existence can easily be accessed. These results are compared with data obtained from bulk samples.

The understanding of the structure and the stability of high entropy alloys is still incomplete and the mechanism behind the composition-property relationship is unclear. One reason is that few systematic and accurate determinations of the composition-dependent structure on the atomic level and of the physical properties have been made. In this paper we report on the structure and physical properties of CoCrFeNi and CoCrFeNi-X, (X=Pd, Sn, Ru) alloys of equimolar composition using different experimental techniques (microscopy, neutron and X-ray diffraction, atom probe tomography, Mössbauer spectroscopy, calorimetry). The results show that i) the alloys are not completely homogeneous as is generally suggested in existing literature; ii) they do not form a perfect solid solution; iii) their structure is not single phase, even not either fcc or bcc.

Recently developed high entropy alloys (HEAs) have complex chemical composition, however, the relationship between the choice of constitutive elements and their concentration and phase composition and microstructure of HEAs is not fully understood at the moment, as well as the potential effect of annealing on the phase composition of HEAs. In this report, we present data on microstructure of the CoCrFeNiMn-based alloys with different V content in as-solidified state and after annealing at temperatures of 700–1000°C. It is shown that alloying with V results in formation of intermetallic sigma phase in as-solidified state. Annealing has pronounced effect on morphology and volume fraction of sigma phase. The temperature corresponding to maximum volume fraction of sigma phase is shown to be significantly dependent on V concentration.

A study on effect of boron addition on microstructure and property of low cost beta Ti-Al-Cr-Fe-B alloys are undertaken in the present. The Ti-Al-Cr-Fe alloys were developed as low cost beta Ti alloys for automotive springs, based on Molybdenum equivalency. Low priced Cr-Fe master alloys were introduced as beta stabilizing alloying elements for lowering cost, and elastic modulus. The boron addition is introduced in to refine the ingot microstructure and thus simplify hot working, which should lead to a cost reduction. On the other hand, the Ti-B compositions are able to restrict beta grain growth during heat treatments. So it can increase strength and microstructural stability. The mechanical tests show that the boron modified alloy has good tensile properties in solution condition. Moreover, the alloy can obtain well-balanced high strength levels with acceptable ductility after modulated aging treatment.

Intermetallic γ-TiAl based alloys have sought-after good high temperature specific strength and creep resistance; however, their low room temperature ductility presents significant design challenges. A better balance of mechanical properties may be achieved with proper microstructure optimization. Microstructure-sensitive structure-property modeling allows for this optimization to be done faster and less expensively, through the use of finite element simulations. Three modeling tools are required for microstructural modeling: microstructure generators to re-create statistically realistic microstructures, crystal viscoplasticity constitutive equations implemented for use with finite element solvers, and post-processing tools to evaluate important mechanical properties and fatigue at a variety of microstructural features. A preliminary investigation into the development and application of these tools is reviewed here for a γ-TiAl based alloy known as a TNM alloy, which has a triplex microstructure.

Ti-1023 alloy has been widely used in aerospace field as a typical titanium alloy with high strength and toughness. The relatively high content of Fe causes beta fleck which will make uneven microstructure and less plasticity. The new Ti-Al-Fe-V (Cr, Zr) alloys have been designed, based on Molybdenum equivalency and Bo-Md molecular orbital method, to aim at developing a new type of titanium alloy with high strength and fracture toughness. After primary design computation, Ti-Al-Fe-V (Cr, Zr) alloy was optimized finally. A large scale ingot was made by vacuum arc re-melting (VAR) for further property evaluation. Resultantly, it shows that athermal ω phase forms in Ti-Al-Cr-Fe-V-Zr alloy when solution treated at a temperature above the β-transus. Micro-hardness of alloy conducted to different aging conditions decreases with the aging temperature and time increasing respectively. Moreover, the new alloy has got a more sluggish age hardening response relating to the aging time. Additionally, after modulated aging treatment, the alloy can obtain high strength levels with acceptable ductility. When the alloy solution treated at 770 °C for 1h, followed by aging at 500 °C for 2h, the tensile strength of the alloy can achieve 1268 MPa, with an elongation of 11.5%, at the same time, the reduction of area has surpassed 30%. As a result, the newly designed alloy can achieve a good combination of tensile strength and plasticity through appropriate heat treatment.

To explore fuel systems that are more robust under accident scenarios, the DOE-NE has identified the need to resume transient testing. The Transient Reactor Test (TREAT) facility has been identified as the preferred option for the resumption of transient testing of nuclear fuel in the United States. In parallel, NNSA’s Global Threat Reduction Initiative Convert program is exploring options to replace the existing highly enriched uranium core with low enriched uranium (LEU) core. To construct a new LEU core, fabrication processes similar to those used for the original core must be identified and developed. Initially, graphite matrix fuel blocks were either uniaxially pressed or extruded following historic routes; however, the project expanded to explore methods to increase the graphite content of the fuel blocks and modern resins. Materials properties relevant to fuel performance including density and thermal diffusivity were measured. The relationship between process defects and materials properties will be discussed. LA-UR-14-27588

Nuclear fuel rods in power reactors are typically clad with zirconium based alloys. These materials undergo corrosion and consequent hydriding during reactor operation. Due to limited storage space in the utilities’ spent fuel pool for used and discharged fuel, many of the utilities are implementing dry cask storage. There is a concern that the relatively high temperature drying process for dry storage coupled with the nascent hydrides and internal gas pressures, may promote radial hydride reorientation that is favorably oriented to promote clad cracking clad breach during storage, transport and handling. Samples were charged with 200 and 800 wppm gaseous hydrogen and subjected to a radial hydride growth treatment at three stresses. These samples were characterized and tested using a simple ring compression test. Ductile to brittle transition temperatures were determined for these samples.

The X12(12CrMoWVNbN) steel is used in ultra-supercritical steam turbine rotors, which play a crucial role in the large nuclear power plant. However, the quality of the heavy ingots has been commonly affected by their solidification structure. One of the most typical defects is the centerline shrinkage porosity. With this context, a 50×120mm X12 steel ingot was cut and polished. The distribution and size of the shrinkage porosity in the section surface was observed and analyzed. On basis of these experimental results, through the FEM simulation several thermal transfer coefficients between the casting and mould wall have been clarified and the suitable coefficient is λ=1000w/(m2 ·k). With this result, the distribution and size of the simulated centerline shrinkage porosity agree well with the experimental results. Subsequently, by the simulation method and results, it is possible to improve the performance for simulate how to eliminate the shrinkage porosity by outfield method.

9–12%Cr ferritic/martensitic steels have been suggested for structural applications in Generation-IV reactors. Because of the high temperatures approaching 823–973 K envisioned in the designs of Generation IV reactors, mechanical behavior of the 9–12%Cr steels at temperatures up to 823–973 K require investigations. Serrated flow in P92 and 11Cr ferritic/martensitic steels was investigated through tensile tests at initial strain rates of 2×10−5−10−3 s-1 at temperatures ranging from 298 to 973 K. Serrated flow occurred at three temperature regions of 298 K, 548–623 K and 773–973 K when tensile tests were conducted at strain rates of 2×10−5−10−3 s−1. There appear to have no previous reports on the serrated flow found in 9–12%Cr ferritic/martensitic steels at temperatures higher than 823 K. Activation energy for the occurrence of serrated flow at temperatures around 573 K (558–623 K) and around 923 K (873–973 K) was determined to be about 126.5 and 43.44 KJ/mol, respectively. The mechanism of serrated flow in the steels was discussed.

A bending fatigue mini-specimen (Krouse type) was used to study the fatigue properties of nuclear materials for (SS304L, HT9). The objective of this paper study fatigue for HT9 ferritic-martensitic steel and SS304L using a mini-specimen (Krouse type) suitable for reactor irradiation studies. These mini-specimens are similar in design (but smaller) to that described in the ASTM B593 standard. A bending fatigue machine was modified to test the mini-specimen. This study was conducted to evaluate the high cycle bending fatigue behavior of HT9 and SS304 and compare its bending properties with simulations conducted with the Abaqus FEA code. Other properties including tensile strength and hardness were also measured. The S-N fatigue results were affected by polishing of surface and bending fatigue reported values for HT9 were lower than the typical S-N curve for SS304L.

Slow strain rate tests for sensitized, solution annealed 304, and solution annealed cooled in air and welded, several sensitized and cold worked 304L stainless steels at 288 °C were carried out. Intergranular stress corrosion cracking IGSCC and Transgranular Stress Corrosion Cracking (TGSCC) were found in sensitized 304 stainless steel and only TGSCC was found at solution annealed 304 and 304L in all metallurgical conditions. The results are discussed based on previous results of residual strain and cracking in real core shroud welds and the qualitative role of residual strain is associated to the susceptibility to TGSCC in low sensitized stainless steel.

Three-dimensional models coupling fluid flow, heat transfer, magnetic field and solidification for steel continuous casting process with FC-Mold were developed to calculate the growth of the solidification shell, which considered the washing effect of fluid flow on the solidified shell and proposed an entrapment criterion for inclusions. The results show that the FC-Mold decreases the flow velocity in the center of the mold and the area of solidification front with a flow velocity larger than 0.07m/s. The inflow jet from the outport nozzle of the submerged entry nozzle suppresses the growth of shell near the impinging point. The predicted distribution of inclusions within surface layer considering the washing effect of fluid flow is in good agreement with the experimental results. The FC-Mold improves the removal of inclusions on the top surface from 2.5% to 3.5% under the same casting conditions.

Based on the mathematical model, this study investigated the process of electro-slag remelting. Maxwell equations are firstly solved to calculate the magnetic field and the distribution of joule heating. Then these two terms are implemented in momentum and energy equations via “User Defined Functions” in FLUENT. The Volume of Fluid method and the enthalpy-porosity approach are applied to capture the multiphase flow and the melting process. The magnetic field, the resulting Lorentz forces and the joule heating are modeled assuming they are independent of the flow. The results show that the molten steel film can generate at the tip of consumable electrode and converge into droplets which fall down through the slag bath and into the liquid metal pool. In addition, an intense non-axisymmetric flow occurs that cannot be realized by conventional two-dimensional model.

A micromechanics model has been developed for predicting effective hygrothermoelastic properties of composite materials and recovering the local fields within the unit cell. Starting from the functional of free energy, a variational statement governing the micromechanics model was formulated through an asymptotic expansion of the functional of free energy. Finite element method was employed to solve the fluctuation functions, which in turn were used to obtain the effective material properties and to recover the distributions of the local fields. Numerical examples were used to validate the theory and the code.

Phase-field simulations of the martensitic transformation (MT) with plastic deformation are carried out. The elasto-plastic phase-field approach of semicoherent MT is used. The evolution equation for the dislocation density field is extended by taking into account the thermal and athermal annihilation of the dislocations in the austenitic matrix that leads to an inhomogeneous distribution of the total dislocation density. During the phase transformation one part of the dislocations in the austenite being responsible for the plastic strain is inherited by the martensitic phase and this inheritance depends on the kinetics and the crystallography of the MT. Another part of dislocations moves with the transformation front and decreases the total plastic strain. Based on the simulation results the specific type of phenomenological dependency between the inherited plastic strain and the martensite phase fraction is proposed.

During high temperature creep or more complicated tests requires data on the actual volume fraction of Gamma Prime phase, as well as the internal stress state and plastic strain of each phase, mobile dislocation densities…This can be obtained at a few minutes intervals by a combination of high resolution synchrotron XRD at the high energy beamlines of the ESRF or DESY and in situ HT mechanical testing. We present here experimental results obtained during tests between 950°C and 1160°C involving either stress jumps or temperature excursions. In both cases, the Gamma corridors exhibit a threshold behaviour related to the Orowan stress. The strain rate of the Gamma Prime rafts does not only depend on the applied load, but even more on the actual value of the stress component perpendicular to the tensile axis.

Recrystallization, which can be ascribed to the plastic deformation, poses one of the major difficulties in post-processing of SX blades castings of Ni-based superalloys. Hot compression and Brinell Indentation were utilized to cause plastic deformation, and thereafter some received solution heat treatment at different temperatures for different time. Profiler observation of indented deformation confirms the anisotropic mechanical properties of single crystal Ni-based superalloys. Deformation at high temperature leads to high dislocation density and stored energy, increasing the propensity of recrystallization, which is revealed by TEM and EBSD analysis. Critical temperature is relatively higher for SX superalloys than DS superalloys, and decreases with increasing plastic strains. Besides, it’s easier for nucleation and grain boundary migration in the dendrite core region, which corresponds to the microsegregation and difference of γ’ morphology between dendrite stern and eutectic regions.

Bromobutyl rubber (BIIR) is an isobutylene/isoprene copolymer, containing 1.9% to 2.1% bromine content. Halogenated butyl rubbers have their major applications in tires without inner tubes, various types of seals, membranes, hoses for chemical products conveying and stoppers for pharmaceutical uses. Bromobutyl rubber, when exposed to high radiation energy show two chemical effects: crosslinking and chain-scission with further degradation, prevailing chain-scission. In case there is build-up of insoluble gel, crosslinking will be predominant. Doses used in degradation study via gamma ionizing radiation were: 25 kGy, 50 kGy, 100 kGy, 150 kGy and 200 kGy and there were assessed changes in principal properties. Compounds of bromobutyl rubber showed significant radio degradation above 100 kGy. Doses higher than 100 kGy imparted changes in mechanical properties, due to degradation caused by gamma irradiation.

In this paper, in order to optimize process and improve the performance of LiNi_1/3Mn_1/3Co_1/3O₂ coin-type lithium ion battery, the significantly influential factors were screened by orthogonal test. The technological conditions such as acetylene black%, PVDF%, drying temperature and drying time were investigated. The main experiment target include capacity retention rate at 0.2C and 1C. The optimal technological condition combination of LiNi_1/3Mn_1/3Co_1/3O₂ coin-type lithium ion battery was obtained by orthogonal analysis.

An environmentally friendly sodium transition metal phosphate (NaMn_1/3Co_1/3Ni_1/3PO₄) has been synthesized via combustion route with carbon coating on the surface. Energy storage devices based on sodium have been regarded as an alternative to the traditional lithium-based system because they are abundant in nature, inexpensive and safe. Sodium transition metal phosphate served as an active electrode material for both aqueous and nonaqueous hybrid supercapacitors. The electrochemical behavior of phosphate vs. activated carbon in the fabricated hybrid device exhibits both faradaic and nonfaradaic processes. Reversible Na+ de-intercalation/intercalation and desorption/adsorption occur within a safe voltage window for both aqueous and nonaqueous electrolytes. The asymmetric device shows redox peaks in the cyclic voltammetry and sloping profiles in the charge-discharge curves while providing excellent capacity retention. A detailed study on the electrochemistry and materials perspective (using microscopy and surface analyses) with an emphasis on the reaction mechanism has been reported.

The pn-junction Charge Couple Device - pnCCD - is a versatile detector which offers the possibility to perform Energy-Dispersive X-ray Diffraction (EDXD) experiments using white Xray radiation. Because the point of impact on the detector area and the energy of a photon event is measured simultaneous EDXD allows for sample characterization without sample alignment or time-consuming rocking a sample, i.e. sample can be characterized by “one-shot” exposure. As an example for its application in material science we show an EDXD experiment performed at duplex stainless steel specimen treated by Very High Cycle Fatigue (VHCF). Probing the specimen in transmission geometry data acquisition could be realized within few seconds in an energy range between 5–40 keV. Due to the grain structure of sample various streaky Laue peaks appeared. Intensity and extension of the Laue streak varies as function of the position across the sample. Evaluating the intrinsic structure of Laue streaks it was found that the energy varies as position along the Laue streaks. Whereas for most of the detected Laue streaks their energy dependence follows Bragg´s law major deviations have been found at spatial positions of a crack formed due to VHCF treatment. This makes the EDXD method suitable for fast indication of defects positions along the sample.

A pure Fe and a binary iron carbon alloy were examined using neutron diffraction in a high flux magnetic field to characterize the influence of the field on the equilibrium allotropic phase transformation. Previous literature indicated the transformation of a common steel alloy from ferrite to austenite increased by 3°C per tesla applied. This work found that this common alloy was not typical for all commercial steels, however the change was found to be consistent across hypoeutectoid carbon levels. A change in the normal hysteresis between heating and cooling was measured, as the magnetic field favored the ferromagnetic phase. The measured temperature change was related to the corresponding change in Gibbs free energy and its reduction of the stable critical nucleus size, which predicts finer grain sizes and lath spacings when steel is subjected to a field during a phase transition. This allows the Hall-Petch relationship to explain the enhanced physical properties seen using this technique.

With scaling beyond 40um pitch 3D interconnects, cost, performance and reliability become ever more critical. Thiol-based self-assembled monolayers (SAM) were applied before to enable Cu-Cu connection in dual damascene vias [1]. In this study, we are researched a parallel application, for an alternative, low-cost organic surface finish for electroplated Cu pads/pillar/bumps to enable 3D interconnects [2]. The effects of pre-cleaning, deposition times and self-assembled monolayer (SAM) type (C3, C10, C18) on oxidation resistance and electrical continuity were studied with Voltammetry and X-ray Photoelectron Spectroscopy (XPS). Experiments were performed on electroplated Cu flat samples and process conditions were selected for further processing of 3D patterned dies and subsequent stacking and thermo-compression bonding in a face-to-face configuration. Overall, C18 SAM showed better electrical continuity and lower electrical resistance than C3 and C10, a result which is consistent with the longer C chain and higher thermal stability of C18. A second result of this study — consistent in both flat and patterned samples — was that microwave plasma cleaning prior to SAM deposition was more effective than wet cleaning, indicating either better oxide cleanability or better affinity of SAM’s with more pristine Cu.

The crystal nucleation and free dendritic growth during solidification is the key factor in determining the microstructure evolutions and morphology. Microscopic simulation using available nucleation and dendritic growth models can be a useful tool for understanding and controlling of such evolution. The present study was conducted to simulate the solidification microstructure formation of Fe-0.4wt.%C alloy using the CALCOSOFT software based on a 3D cellular automaton-finite element (CAFE) method. The two kinds of free dendritic growth models, the LGK model and the KGT model, were used respectively to describe the dendrite growth kinetics in solidification process. The effect of convective heat transfer coefficients on the microstructure was also studied. The calculated results showed that more columnar grains appear with the convective heat transfer coefficients increasing in spite of using different growth models. The simulated results are different under lower convective heat transfer coefficients, but when the convective heat transfer coefficient increases, the results are similar.

As for studying the segregation of elements and the phase transition in the solidification process of the AISI 301 austenite stainless steel, the Differential Thermal Analysis was used to perform the quenching experiment. Under the industry cooling rate (25K/min), the phase transition process of 301 austenite stainless steel is analyzed, and effect of cooling rate on the latent heat release and the alloy elements distribution in the process of solidification is discussed. The results show that the solidification process of the 301 stainless steel start from the precipitation of the δ ferrite, then growing up and the gradual dissolution after the peritectic reaction. The amount of the ferrite approximately goes down 23% from the 1619K to room temperature. In the process of phase transformation, the maximum segregation is existed in the liquid phase and the interface of the any different two phases.

Using classical molecular dynamics simulation together with a modified many-body embedded atom model (MEAM) potential, we simulated the crystallization of supercooled liquid magnesium. Firstly, we analyzed the crystalline structure and some thermodynamic quantities to examine the validity of the potential for the crystallization of magnesium. Then, using averaged bond-orientational order (ABOO) parameters to characterize atoms, we found that the liquid atoms always transform firstly to the metastable body-centered cubic (BCC) atoms and then to the stable hexagonal close packed (HCP) atoms. This demonstrated the applicability of the Ostwald step rule to magnesium. Besides, we found the averaged bond-orientational order parameters Q ₆ of BCC atom was closer to liquid atom than HCP atom, which may explain the phenomenon of forming BCC firstly instead of HCP from liquid to some extent.

Diffusion-couples of pure Fe/Fe-40at.%Cr alloy were used to analyze the phase decomposition process in Fe-Cr alloys. Diffusion-couples were solution treated at 1050 °C for 1 h and subsequently aged at 475 and 500 °C for 1–1000 h. Interdiffusion zones were analyzed by HR-TEM and hardness measurements. The EDS-SEM analysis of solution treated, water-quenched and then aged diffusion-couple permitted to obtain the equilibrium composition of miscibility gap at 500 °C to be 14 at. % Cr. The HR-TEM analysis of the aged diffusion-couple showed the change in size and volume percentages of precipitates with composition. The hardness measurements of the aged diffusion-couple indicated the age hardening due to the presence of nanometric Cr-rich precipitates in a Fe-rich matrix.

In this study, the main target is to obtain the better combination of strength and ductility by using heat treatments to adjust the microstructures of Fe-1.7Mn-1.3Al-0.5C steels. Effect of intercritical annealing (IA) and bainitic holding temperatures on the volume fraction and carbon content of retained austenite were evaluated by means of X-ray diffraction (XRD). Mechanical properties of the steel under different heat treatments processes were investigated by using uniaxial tensile tests. An excellent combination of strength and ductility has been obtained for the steel after intercritical annealing at 800°C for 120s and bainitic holding at 380°C for 300s, revealing a yield strength of 680 MPa, a tensile strength of 1200 MPa and a elongation-to-failure as high as 0.52. The steel mainly consists of ferrite, bainite, and retained austenite. The volume fraction of retained austenite is 28%, with a concentration as high as 1.71%, which enhances the mechanical stability of austenite and results in a good combination of strength and ductility.

Several industrial alloy systems benefit from or try to avoid the precipitation of second phases. With computational thermodynamics techniques, both the bulk thermodynamics and the diffusion issues are currently well modeled for many systems. Recently, the classical models for nucleation and growth have been coupled with CALPHAD tools creating powerful models, which are very effective in many precipitation calculations. However, classical nucleation and growth models consider interfacial energies and these are not well known in many cases. In this work, calculations in industrial systems- mostly steels- are presented highlighting the importance of this variable on the modeling results and some of the current limitations related to the accessibility to the values of this parameter and its temperature dependence. Some reasons for these difficulties are discussed and possible avenues to solve this problem are brought to discussion.

Microstructure development in medium-carbon dual-phase steels depends on various phase transformations depending on initial microstructure and cooling. Dual-phase steels may contain small amounts of retained austenite and bainite as well austenite and ferrite. In this study, intermediate quenching applied to medium-carbon hot rolled steel. The microstructures were characterized using field emission scanning electron microscopy and focused ion beam scanning electron microscopy. Microstructural investigations show that two different types of martensite morphology can be found in microstructure as martensite island and martensite fibers. During the annealing, the nucleation of austenite may occur along the lath boundaries, in martensite laths, blocks and packets as well as prior austenite grain boundary. It is concluded that martensite islands were nucleated at prior austenite grain boundary, while martensite fibers nucleated at martensite laths. Granular bainite was also observed at the boundaries between martensite islands. DICTRA software was applied to understand formation of granular bainite by means of elemental distribution.

In dual-phase steels, partial austenization may result in different volume amount of austenite depending on intercritical annealing temperature between Ac₁ and Ac₃ temperatures. The annealing temperature is also responsible of chemical composition and grain size of austenite. This study deals with the effect of intercritical annealing temperature on M_s for dual-phase steels. In experimental studies using dilatometer, the specimens were first quenched to form martensite from austenitizing temperature of 1100°C. After martensitic transformation, specimens were annealed at different intercritical temperatures and finally gas quenched again. M_s were measured with using dilatometer curves and compared to calculated values using empirical formulas. Grain sizes of final microstructures were also quantitatively analyzed. It was seen that M_s depend on the intercritical annealing temperature. It is concluded that this double effect is attributed to intercritical annealing temperature which is responsible for chemical composition and grain size of austenite.

This study deals with the effect of initial microstructure on final microstructure of medium-carbon dual-phase steels by two different annealing methods. In experimental studies, initial microstructures martensite and ferrite+pearlite annealed at same annealing temperatures and quenched applying different annealing durations. The influence of initial microstructures on microstructural evolution is studied using scanning electron microscope (SEM). The manganese distribution in ferrite and martensite is analyzed by energy-dispersive X-ray spectroscopy (EDS). The experimental study was supported by phase field modeling using Thermo-Calc and Diffusion-Controlled TRAnsformations (DICTRA) softwares. Experimental results showed that dual phase microstructure has inhomogeneity of martensite islands and fibers in ferritic matrix after intermediate quenching. Martensite formation occurred at prior austenite grain boundaries and martensite laths. In the case of intercritical annealing, pearlite regions are transformed to austenite and eventually martensite islands after quenching.

High-energy ball milling was used to produce a partially alloyed elemental nickel and molybdenum of Ni₃Mo composition, cold-compacted and then sintered/solutionized at 1300°C for 100 h and quenched. Three transformation studies were performed. First, the intermetallic γ-Ni₃Mo was formed from the supersaturated solution at temperatures below the peritectoid isotherm. Cellular precipitation was observed in some samples. Second, the reversed peritectoid transformation from γ-Ni₃Mo to α-Ni and δ-NiMo was performed. Regardless of heat-treatment temperature, samples heat-treated for short times exhibited small precipitates of δ-NiMo along and within grain boundaries of α-Ni phase. Third, the transformation from the supersaturated solution to the peritectoid two-phase region was performed. Precipitates of δ-NiMo were observed and additionally, spinodal structure with compositions of 14 and 24 at. % Mo developed in the solid solution matrix for most samples. In all three cases, hardness values increased and peaked in a way similar to that of traditional aging, except that the peak occurred much rapidly in the second and third cases.

Fe-50%Ni alloy is widely used in industrial fields as its excellent magnetic performance, and the average grain size has a strong effect on magnetic performance. In this paper, Fe-50%Ni alloy specimens are annealed under the hydrogen protection and vacuum respectively at different temperatures and holding times. Metallographic observation and grain size measurement are both finished. The metallographic observation shows that grains grow up more easily and fast under the hydrogen atmosphere than in vacuum. Hydrogen can reduce the chemical activation energy, and decrease the impurity elements more easily. A new model is proposed to describe the grain size basing on the assumption that <math display='block' xmlns='http://www.w3.org/1998/Math/MathML'> <mrow> <mover accent='true'> <mrow> <msup> <mi>D</mi> <mn>2</mn> </msup> </mrow> <mo stretchy='true'>&#x00AF;</mo> </mover> <mo>&#x2212;</mo><mover accent='true'> <mrow> <msubsup> <mi>D</mi> <mn>0</mn> <mn>2</mn> </msubsup> </mrow> <mo stretchy='true'>&#x00AF;</mo> </mover> <mi>&#x03B1;</mi><msup> <mi>t</mi> <mi>m</mi> </msup> </mrow> </math>$$\overline {{D^2}} - \overline {D_0^2} \alpha {t^m}$$ by experiments and <math display='block' xmlns='http://www.w3.org/1998/Math/MathML'> <mrow> <mover accent='true'> <mrow> <msup> <mi>D</mi> <mn>2</mn> </msup> </mrow> <mo stretchy='true'>&#x00AF;</mo> </mover> <mo>&#x2212;</mo><mover accent='true'> <mrow> <msubsup> <mi>D</mi> <mn>0</mn> <mn>2</mn> </msubsup> </mrow> <mo stretchy='true'>&#x00AF;</mo> </mover> <mi>&#x03B1;</mi><msup> <mi>e</mi> <mrow> <mo>&#x2212;</mo><mstyle scriptlevel='+1'> <mfrac> <mi>Q</mi> <mrow> <mi>R</mi><mi>T</mi> </mrow> </mfrac> </mstyle> </mrow> </msup> </mrow> </math>$$\overline {{D^2}} - \overline {D_0^2} \alpha {e^{ - \tfrac{Q}{{RT}}}}$$ by thermo dynamical theory. The fitting result shows that the new model can describe the grains growth process better than the classical one.

Fe-Mn based alloy has the potential as “third generation” advanced high strength steels (AHSS) for automotive due to its excellent comprehensive properties. The present paper considered the structure and phase transition of Fe-2Mn alloy gas-atomized powders. It was found that only bcc structure ferrite obtained when the temperature was at room temperature, then the ferrite ➛hcp-ε phase ➛ γ-austenite and ferrite ➛γ-austenite phase transition was triggered with the temperature increasing. Results of Differential Scanning Calorimeter (DSC) measurement showed that the ferrite ➛ε and ferrite ➛ austenite phase transition occurred at 858°Cand 910°C, respectively, transition from e phase to γ-austenite occurred at 1158°C. Dynamics analysis was conducted on solid phase transformation, nucleation and the free energy of solid phase transition were calculated, aimed to clarify the solidification process.

A universal scaling of subgrain size evolution in face-centered cubic (fcc) metals with moderate to high stacking fault energy is proposed for a class of deformation processing applications based on severe plastic deformation inherent to chip formation in Plane Strain Machining (PSM). The complex trajectories of grain refinement followed by PSM are captured using two parameters — the effective strain and the parameter “R” that is a function of the strain-rate, temperature and material dependent constants. Proposed parameterization entails a weak contribution of strain and “R” interaction which enables examining the athermal evolution of subgrain size. This approach yields that the subgrain size behavior, under the PSM thermomechanical conditions, obeys a universal scaling law while scanning along the strain levels.

Refractory materials are critical for the ultra-high temperature environments that are encountered in diverse settings, from turbine blades to the leading edges of objects travelling at hypersonic speeds through the atmosphere, such as railgun projectiles or reentry craft. Hafnium carbide and hafnium diboride are refractory materials with melting points in excess of 3200°C. Our goal is to develop a versatile polymer precursor-based route to produce hafnium carbide and hafnium diboride using reductive techniques to couple haloform monomers and oxidative methods to couple borohydride monomers. The flexibility of the system we describe will also enable us to produce hafnium carbide and tantalum carbide solid solutions, which possess the highest reported melting point of any refractory, >4200°C. Critically, these polymeric precursors will provide potential pathway for producing conformal, thin and thick films suitable for the leading edges of hypersonic projectiles or reentry craft.

Hydroxyapatite (HAP) is the most researched calcium phosphate material in the field of biomaterials to be used for bone re-engineering applications; given its attractive properties. Plasma spraying is the best available industrial method that can be used to deposit HAP coatings on metallic substrates. However, this process is sustained with high heat inputs which decompose HAP into secondary phases. These phases are undesirable for biomedical applications. Lasers are sued as secondary post-laser curing step where they are used to improve the crystallinity of these coatings. The purpose of this study was to establish the optimised setting process parameters necessary for direct laser melting process. Nd-YAG laser was used to directly melt HAP powder beds preplaced on Ti-6Al-4V. The produced coatings were characterised with preserved, mixed morphologies of HAP crystallites that sat on the surface of the coating. These crystals were suspended on the long and short titanium needles according to SEM images. XRD results indicated a mixture of HAP and TTCP in the coating while TEM conclude a hexagonal atomic packing. These results indicated that in addition to laser power and scanning speed, the angle at which the laser beam interacts with material is also a necessary parameter to optimise.

Ceramic particles like SiC have attracted great attention because of their usability as reinforcement for composite materials. Autocatalytic (electroless) nickel deposition is a unique process for the enhancement of the surface properties of ceramic particles. In this study, deposition of nickel phosphorus (Ni-P) and nickel boron (Ni-B) layer on SiC particles via autocatalytic plating in hypophosphite and borohydride baths was investigated. SiC powders were sensitized and activated respectively in order to ensure catalytic properties. Electroless nickel coating was carried from two different nickel ion sources (nickel chloride, nickel sulphate) following the pre-treatments of particle surfaces. Coated powders morphologies were characterized by transition electron microscope (SEM). X-ray diffraction and energy dispersive spectroscopy (EDS) analysis were used to investigate the chemical analysis of coating layers. The results showed that a better uniformity and bonding were obtained for Ni-P coatings with the Ni source of NiSO₄.6H2+O as compared to NiCl₂.6H2+O. For Ni-B coatings, the Ni2+ source of NiC₁₂.6H₂O has provided better quality and continuous coating layer on SiC surfaces.

Ultra-fast surface hardening of low carbon steel is introduced via the application powder-pack boriding process in a hot isostatic pressing special fixture. Boriding (Boronizing) powder consisting of boric acid and borax mixture is utilized in 50 wt. % boric acid and 50 wt. % of borax. Low carbon steel sample packed with boric acid and borax, heated at 1050°C for 30 minutes and then at tempered 900oC for 30 minutes in a special fixture sealed with a 10 Ton pressure. The surface boride layer as FeB and Fe₂B phase with the hardness about ~1800 HV and depth of 130–180 μm is achieved and compared to untreated base metal of 123 HV. Alloy segregation along with delocalized zone of interest is achieved with different boron content 1.77 wt. % along grain boundaries, 3.93 wt. % leading phase and 7.86 wt. % trailing phase at the sample surface. This process provides high performance and high thickness of coatings and can be used fast and economically if compared to traditional processes with less emission. From economic and environmental points of views, it is highly desirable to develop and implement novel surface treatment technologies that are quick, cheap, clean, and energy efficient.

The reactive diffusion layer between solid Fe-Mn and liquid 55Al-Zn-1.6Si (Galvalume, GL) was experimentally observed using Fe-Mn/GL diffusion couples. The diffusion couples were prepared by vacuum sealed technique and then immediately annealed at temperatures of T=873 K for various times up to t=2h. During annealing, a compound region consisting of Fe₂Al₅ and FeAl₃ and T₅ intermetallic compound is formed at the interface in the diffusion couple. The thickness is much smaller for the FeAl₃ layer than for the Fe₂Al₅ and layer. Comparative study the influence of different content of alloy elements manganese on the interface reaction layer, The interfacial reaction layer thickness is getting thinner with the increase of manganese content. Through the first-principles method gives a theoretical explanation for this phenomenon.

Asymmetric membranes, with suitable mechanical properties under working conditions, lead to an enhanced oxygen permeability compared to self-supported membranes. In this work, crack-free asymmetric tubular membranes made of BaCo_0.7Fe_0.2Nb_0.1O_3-δ perovskite oxide were prepared via a dip-coating and co-sintering method. The crystal phase of the top layer of asymmetric membranes prepared was the same as that of powders, which were of the cubic perovskite phase. The thickness and quality of the dense layer can be controlled by adjusting the concentration of the suspension slurry in the range of 10–50 wt%. Moreover, dip coating repeatedly is helpful to ensure the integrity of the membrane. The microscopic structure of membrane was characterized by SEM which showed that the top layer of asymmetric membrane was dense and crack-free. Notably, when tested for oxygen separation, the oxygen flux of asymmetric membrane was significantly higher than that of self-supported membranes.

The aim of this study is to discover the enamel substrate adhesion mechanism. Enamel is composed of organics in oxide forms, applied on a metal substrate with a firing temperature range of 800–870°C. Most important factors that affect adhesion of the enamel to the substrate are; enamel composition, firing time, substrate-enamel compatibility and surface roughness of the substrate. Adhesion mechanisms can be explained by 3 base theories; chemical, mechanical and diffusion. This study focuses on examining adhesion mechanisms between enamel coatings and substrates. During laboratory studies, enamel composition variations were investigated for explaining chemical theory; different samples with different surface roughness values were observed via different characterization techniques in order to explain mechanical theory. Adhesion of enamel to the substrate was scaled via SEM and impact tests. It is concluded that; cobalt oxide presence in enamel composition promotes adhesion; adhesion ability deteriorates with lowering cobalt oxide volume. It is proved that; the increment in surface roughness also increases adhesion quality. It is established via SEM analysis that; the dendritic formations along the enamel-substrate interface are oxidation of metal that fuses through enamel.

Alloys of tungsten 20% manganese 17% titanium and tungsten 18% manganese 17% chromium (at%) were prepared by mechanical alloying and sintering from 1225 to 1425°C. The microstructures were examined by XRD and SEM/EDS. In the titanium-containing alloy, XRD patterns revealed peaks related to TiN and MnTi₂O₄. In the chromium-containing alloy, peaks related to a chromium-rich phase and MnCr₂O₄ were observed. SEM backscattered images of the titanium-containing alloys depicted two distinct phases: a tungsten-rich phase and a manganese-titanium oxide. The addition of titanium increased the solubility of manganese in the tungsten-rich phase, compared to tungsten-manganese alloys, to 6.3 at% Mn with 3.9 at% Ti after sintering at 1275°C for 30 min. Alternatively, the addition of chromium produced no significant improvement in the solubility of manganese; however, the solubility measurements were more consistent. Although the microstructural constituents of both alloys underwent grain growth at higher sintering temperatures, the microstructure remained relatively fine.