The influence of prior-deformation on the mechanical and electrical properties of Cu-4.2 mol% Ti alloys aged in a hydrogen pressure of 0.8 MPa was examined. This follows from the results of aging solution-treated Cu-Ti alloys in a hydrogen atmosphere, which significantly improved their electrical conductivity over alloys conventionally aged in vacuum, without degradation of the mechanical strength. The maximum-strength was enhanced in the prior-deformed specimen, and the strengthening and increase in electrical conductivity were accelerated during aging in a hydrogen atmosphere, compared to that for the non-deformed specimen. As a result, the balance between the strength and the conductivity is improved within shorter aging time for specimens that are more severely deformed and then aged in a hydrogen atmosphere. The strengthening is mainly due to age-hardening by the growth of finely dispersed precipitates of Cu₄Ti and TiH₂, which are preferentially nucleated at lattice defects such as dislocations and nano-sized deformation twins. The improved conductivity is closely related to reduction of the solute Ti concentration in the copper matrix, which is attributed to the precipitation of TiH₂ and Cu₄Ti. Thus, prior-deformation assists to render a good combination of strength and electrical conductivity for Cu-Ti dilute alloys during aging in a hydrogen atmosphere.

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The effects of the second pulse in resistance spot welding (RSW) on the mechanical properties of dual phase (DP600) steel were investigated. The experimental results show that the addition of the second pulse can give rise to the formation of acicular ferrite, retained austenite and chromium carbides, which can markedly improve the cross-tensile strength (CTS) comparing to that treated by the single pulse technology. Meanwhile, the formation mechanism of acicular ferrite, bearing the cubic to cubic orientation relationship with respect to the surrounding martensite lath, was revealed by the analysis of the thermal history of DP600 steel under different RSW processes. The effect of microstructure on the fracture behavior was also discussed.

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Dislocation densities in 10Cr-5W low-carbon steel that containing carbon content is 0.02C, 0.03C, 0.09C and 0.13C mass% were determinedd from X-ray line analysis based on the modified Williamson-Hall and Warren-Averbach methods. In the as-quenched state the dislocation density in the martensite phase increased with increasing carbon content for these low-carbon steels.

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Diffusion-couples of pure Fe/Fe-40 at%Cr alloy were used to analyze the phase separation process in Fe-Cr alloys. Diffusion-couples were solution treated at 1050°C for 3.6 ks and subsequently aged at 500°C for 3.6–3600 ks. 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.

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A square steel pipe is reshaped from a welded round pipe by roll forming. We investigated the effect of the roll diameter on the cross-sectional size of the square steel pipe by experimentation and three-dimensional finite element (FE) simulation. When the diameters of the top and bottom roll pairs are larger than those of the pair of side rolls, the cross section width of the formed pipe is less than the height. To equilibrate them, we perform finish forming at the final stage. Furthermore, the width of corner part of the formed pipe is greater than its height. The difference between these two sizes of width and height of the corner part in the final product is greater than those at upstream stands and increases with the ratio of the diameter of top and bottom roll pairs to that of side roll pairs. Offset the smaller roll pairs upstream makes the pipe square. Such offset is effective for producing pipes with equal width and height at the corner.

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By using chemical vapor infiltration (CVI) method, 2.5D C/SiC composites were obtained with an average flexural strength of 213.8 MPa, matching the requirements of thermal protection application. Tests of coefficient of thermal expansion (CTE) indicated that The CTE of the 2.5D C/SiC composites remained at a relatively low level (below 2.5×10⁻⁶ K⁻¹) in the whole temperature range, which may be attractive for applications that required good dimensional stability. The relationship between the CTE and the temperature was also discussed.

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This study examined the possibility of surface heat treatment by the plasma electrolysis from phosphate electrolytic solution on magnesium alloys. Effects of the anodic plasma electrolysis onto various AZ series magnesium alloys on the mechanical properties and microstructure were examined.
The tensile test revealed that the anodic electrolytic treatment at final bias voltage from 250 V to 400 V influenced the tensile strength. The tensile strength of AZ61 and AZ91D substrate after anodic electrolytic treatment increased or decreased, and this change of tensile strength is attributable to the precipitation of intermetallic compound (β phase, Mg₁₇Al₁₂) as sparks occurred due to dielectric breakdown during anodic electrolysis. These results demonstrate the utility of this electrolytic treatment on AZ61 and AZ91D magnesium alloys.

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Compositions with tie lines between the σ and (γ,δ) phases in a ternary Re-Cr-Ni system were investigated by heat treating various ternary Re-Cr-Ni alloys at 1573 K in vacuum for up to 2000 h. The microstructures of the Re-containing alloys that had been water quenched after various heat treatment for times were observed and their concentration profiles for Re, Cr, and Ni were measured using an electron probe microanalyzer. The Re-Cr-Ni alloys consisted of the σ phase with either the γ or δ phase. The concentration profiles of the γ phase became flat after short heat treatment, whereas longer times of up to 2000 h were required to achieve the same effect for the σ and δ phases.
The tie-line composition (at%) of each phase at 1573 K was experimentally determined as follows. The σ phase tie-line with the γ phase (17.3 Re, 20.6 Cr, and 62.1 Ni) consists of 53.1 Re, 25.5 Cr, and 21.4 Ni. The σ phase tie-lined with the γ phase (16.9 Re, 19.2 Cr, and 63.9 Ni) consists of 53.0 Re, 24.6 Cr, and 22.4 Ni. The σ phase tie-line with the γ phase (12.7 Re, 24.8 Cr, and 62.5 Ni) consists of 48.4 Re, 30.9 Cr, and 20.7 Ni. The σ phase tie-line with the γ phase (6.1 Re, 46.2 Cr, and 47.7 Ni) consists of 28.1 Re, 52.3 Cr, and 19.6 Ni. The σ phase tie-line with the δ phase (85.6 Re, 5.2 Cr, and 9.2 Ni) consists of 61.1 Re, 27.7 Cr, and 11.2 Ni.

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A Ti plate coated with an Al foil with a thickness of 100 μm was prepared by using explosive energy. The bonding was momentarily achieved without breaking the Al foil. This Al-coated Ti plate was heated between 898 and 1273 K in the air to investigate interfacial reactions in solid Al/solid Ti and liquid Al/solid Ti states from the viewpoint of diffusion coating for Ti materials. At 898 K, a continuous Al₃Ti layer was formed along the interface. Although the Al foil was almost replaced by Al₃Ti in a holding time of more than 32.4 ks, many defects such as void and crack were observed in the Al₃Ti layer. It is noteworthy that the thickness of the Al₃Ti layer increases in proportion to the holding time in the early stage, and then, to the square root of the holding time. On the other hand, the specimen, which was heated at a temperature above the melting point of Al, showed a porous structure of Al₃Ti via an Al + Al₃Ti duplex state. The holding time to produce the porous structure became short with increasing heating temperature. It is expected that the Al + Al₃Ti duplex structure is more beneficial as a surface coating layer formed by the interfacial reaction. To replace the Al foil region by such a duplex structure, continuous heat treatment was performed between 1023 and 1073 K. There were no defects in the Al + Al₃Ti duplex region on the Ti plate, and its maximum Vickers hardness was approximately 3 times higher than that of the Ti plate.

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A CE meter cup was modeled using a casting simulation software and cooling curves at different points of the casting model were calculated. In setting temp-solid fraction parameters, an Fe-C-Si ternary equilibrium phase diagram was used with a substantive temperature range in the equilibrium phases so that the γ-Fe+G+L phases can be considered. In studying the calculated cooling curve, a rapid temperature drop was found in the cooling curve in the final solidification period. This rapid cooling occurred during eutectic solidification. The structure formed by the rapid cooling was found as chill or D-type graphite because the liquid phase is cooled rapidly to below the eutectic temperature. This rapid cooling may be one of the causes of D-type graphite near the final solidification part of thick iron castings.

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The martensitic transformation temperature in addition to the tensile strength and oxidation resistance, were able to be estimated in the crystal structure map using both parameters of the bond order and d-orbital energy level of elements, for the design of TiNi shape memory compounds. The ternary TiNi–(Cr, Re, Fe, Cu, Al) intermetallics having the objective constructed phase, tensile strength, Ms-temperatures and oxidation resistance, were obtained successfully, by the adjustment of both parameters. It is found that the effectiveness of the d-electrons concept could be judged, for property-control of ternary TiNi intermetallics, as well as metallic materials.

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This study performed repair-welding tests on René 77 Nickel-based superalloy by adopting a Nd:YAG pulsed laser technique, coupled with René 41 filler wire and various welding parameters. After welding, the microstructure evolution, crack behavior and mechanical properties of the welds were determined by a combination of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), and micro-hardness test. The experimental results showed that, due to suffering from different thermal histories during the conduction of the multi-pass welding process, the microstructures within the welds had split into six zones. In terms of cracking behavior, no cracks formed in the weld fusion zone (WFZ) or the heat-affected zone (HAZ) under appropriate welding parameters; however, setting the laser energy too high resulted in weld centerline cracking or intergranular cracking in the weld fusion zone. Moreover, various types of liquation cracks may occur at the interface between the WFZ and the HAZ.

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A dual two-phase Ni₃Al-Ni₃V intermetallic alloy with a nominal composition of Ni_75.0Al_7.5V_15.0Nb_2.5 (at%) doped with 50 mass ppm boron was synthesized by the powder metallurgy process using elemental powders. Raw powder mixture was sintered at temperatures from 1073 K to 1373 K by the pulse current sintering method and then annealed in a vacuum at 1553 K for 3 h. The dual two-phase intermetallic alloy whose microstructure exhibits the cuboidal primary Ni₃Al phase and the surrounding channel region composed of Ni₃Al and Ni₃V phases, and contains neither voids nor intermediate products were obtained by sintering at a high temperature of 1373 K and by subsequent annealing at 1553 K. Also, the well synthesized and annealed samples showed finer grain sizes, i.e., about 30 μm than the cast alloys fabricated by the ingot metallurgy process. The hardness of the synthesized samples increased with increasing sintering temperature and also by the subsequent annealing at 1553 K.

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CO₂ absorption/release properties of limestone mixed with 2.5∼40 mass% reagent grade-SiO₂ powders or natural diatomite have been investigated. XRD analysis of calcined diatomite-mixed limestone revealed the formation of Ca₂SiO₄. However, only CaO and SiO₂ were confirmed in the case of the calcined limestone mixed with reagent grade-SiO₂ powders. Addition of reagent grade-SiO₂ and natural diatomite led to improvement of CO₂ absorption capacity of limestone ore. In the initial absorption process, limestone mixed with 10 mass% reagent grade-SiO₂ showed the highest degree of absorption (67%; 673 K, 21.6 ks). In the case of natural diatomite, CO₂ absorption degree attained maximum (∼55%) at 5 mass% of natural diatomite. Furthermore, the absorption durability of limestone ore was improved by the addition of reagent grade-SiO₂ or natural diatomite. These results indicate that the addition of reagent grade-SiO₂ particles or natural diatomite is an efficient way to improve the absorption properties of natural limestone ore.

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The percolation threshold on a cubic lattice is estimated under a binary distribution of the sizes of the conducting particles. Although we have already investigated a similar size distribution model in 2D (where no drastic change in their percolation threshold was observed) (K. Shida, R. Sahara, M. N. Tripathi, H. Mizuseki and Y. Kawazoe: Mater. Trans. 50 (2009) 2848–2851), a 3D version of this model has not been reported before. In the 3D case, a significant decrease in the percolation threshold compared to the monodisperse cases is observed.

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The Fickian second law is widely applicable not only to the analysis of various diffusion problems in material science but also to that of phenomena for the Brownian motion in other science fields, such as the behavior of neurons in life science. It is thus one of the most dominant equations in science. In 1894, Boltzmann transformed it into an ordinary differential equation applicable to the analysis of the interdiffusion problems. Since then, however, the mathematical solutions have not yet been obtained. Here we derived two new equations superior in calculation to the ones of Fick and Boltzmann. Using the derived integro-differential equation, their solutions were obtained as analytical expressions in accordance with the results of the experimental analysis. Hereafter, the basic equations derived here will be exceedingly useful for the analysis of the nonlinear problems concerning the Brownian motion in various science fields.

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A basic study for the recovery of tin(Sn) from the scraps or plating sludges by a hydrometallurgical process was carried out. Tin was leached out by hydrochloric acid solutions and then separated from the mixed solution of co-leached miner metals such as, As, Sb, Bi, Cu, Zn and Pb for making high purity metal. A solvent extraction process was followed for the separation of tin and other minor metals from hydrochloric acid solution using TBP (tri-n-Butylphosphate) as the extracting reagent. Optimum conditions for the separation process were obtained using separation factors of tin versus each metal impurities derived at various concentrations of hydrochloric acid and sodium chloride in aqueous solution, and TBP in the organic solution. Scrubbing for metal impurities from the loaded organic solution was studied with different HCl concentrations. The study showed that Pb, Bi, Cu, Zn and Sb were quantitatively removed by scrubbing with 8.0 mol/L HCl from the organic phase after extracted in 6.0–7.0 mol/L HCl solution; As with 4.0 mol/L HCl solution from the organic phase after extracted in 3.0 mol/L HCl solution. From the integrated separation experiment by the simulate solution at 25°C, 1.0 of O/A, and one stage contact at each extraction and purification step, the purity of finial Sn strip solution was 98.9% and the recovery of Sn was 67.9%.

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In order to optimize the recovering process of Fe and P from steelmaking slag by the microwave irradiation, heating rates of various substances and recovery ratios of iron and phosphorus from slag-graphite mixtures were investigated. The heating rates of the examined substances are in the order of graphite >> Fe₃O₄ >> Fe₂O₃ > the synthesized CaO-SiO₂-Fe_tO-P₂O₅ slag > the industrial slag. From the maximum heating rates, it was considered that the microwave absorption ability of graphite was 40 times greater than that of the industrial slag. Consequently, it was considered that the heating rate of the graphite-slag mixture was dominantly determined by graphite. In the reduction of the synthetic slag (15 g) by graphite (0.816 g), the weight of the recovered metal was maximized at 900 s under the present experimental condition (1.7 kW, 2.45 GHz). At a fixed microwave processing time of 900 s, the recovery ratio of iron increased with increasing the carbon equivalent (C_eq.: the mole ratio of carbon to oxygen to reduce Fe₂O₃ and FeO, yielding CO gas), and reached 0.97 when C_eq.=1.69. The recovery ratio of phosphorus also increased with C_eq., and showed 0.89 at the same condition. From the chemical analysis of the slag and metal after experiments, it was found that the phosphorus distribution ratio (L_p) strongly depended on T. Fe content in slag, namely, as FeO content decreased, L_p value decreased.

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Microstructure of die-upset Nd-Fe-Co-Ga-B magnet was investigated with a scanning electron microscopy (SEM), high resolution and analytical transmission electron microscopy (HRTEM and ATEM). Inside the original melt-spun flakes in the magnet, the typical texture consists of fine platelet Nd₂(Fe,Co)₁₄B grains surrounded continuously by a thin grain boundary (GB) phase with 2–3 nm in thickness. The GB phase has an amorphous structure of which the chemical composition is Nd₄₄Fe₃₉Co₁₀Ga₇. It was found that high fluidity of the Nd- and Ga-rich GB phase contributes to produce a high crystallographic c-axis alignment of Nd₂(Fe,Co)₁₄B grains. Near the interfaces of the original flakes, morphology of the Nd₂(Fe,Co)₁₄B grains changes from platelet to globular involving the deterioration of c-axis alignment. Many Nd-oxide (NdO and fcc-(Nd,Fe)O_x) grains and a large amount of fine Nd₃Co precipitates are formed near the interfaces, and then the composition of GB phase changes to Nd₃₆Fe₅₀Co₉Ga₅. The insufficiency of Nd in the GB phase and the existence of Nd-oxide particles prevent the anisotropic growth of Nd₂(Fe,Co)₁₄B grains, and then lead to the inhomogeneous GB phase and the low c-axis alignment.

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In-situ sol-gel method was used to prepare TiO₂-coated silica foams by minimizing window (i.e., the part formed by the interconnection of pores) blocking caused from the aggregation of TiO₂ particles during the coating process. Specifically, the coating process employed was achieved by performing sol-gel reaction directly onto the surface of silica foams after penetrating precursor solution through the foams. EDX results showed that TiO₂ particles were evenly distributed onto the surface of inner pores in silica foams, indicating that the coating process employed is likely effective for the surface modification of silica foams with 3-dimensional pore network. Additional characterization tests were carried out to evaluate physical properties (pore structure, crystalline structure, specific surface area, permeability, and mechanical strength) of TiO₂-coated silica foams according to heat treatment temperature (300–1100°C). The anatase phase started to appear at heat treatment temperature of 500°C and had maximum value at 700°C. TiO₂ particles tended to grow with increasing treatment temperature, leading to the change in relevant physical properties (i.e., the decrease in total and open porosity, specific surface area, and gas permeability, and the increase in closed porosity) due to the clogging of micropores (d_p≤2 μm); however, the mechanical strength was enhanced after TiO₂ coating with no significant change with heat treatment temperature.

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The texture development and microstructural evolution have been investigated for the AZ31 alloys rolled by cross-roll rolling at 823 K. After the AZ31 magnesium sheets were rolled by cross-roll rolling at 823 K, the total reduction in thickness of 65% were achieved after two pass rolling. The resultant microstructures are homogeneous and refined for the surface and center layers. The (0002) basal texture is significantly weakened after annealing at 623 K for 1 h for the cross-roll rolled sheets.

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Flakes of Fe_84.3Si₄B₈P₃Cu_0.7 amorphous alloy ribbons with low glass forming ability were consolidated into bulk nanocrystalline specimens (magnetic core shape) with 12 mm in diameter and 2–5 mm in height by the spark plasma sintering (SPS) technique. The SPS technique, capable of rapid heating and cooling, enabled us to obtain a densely compacted bulk nanocrystalline material by maintaining the status of amorphous structure or nanocrystalline structure. As a result, high relative density ∼91.8–96.1% and nanocrystalline structure with average grain size below 41 nm were obtained. The Vickers hardness of the bulk nanocrystalline samples approaches to 1513, which is 2.0 and 3.2 times of the as-quenched amorphous ribbon and the fully annealed ingot, respectively. These sintered nanocrystalline materials exhibit good soft magnetic properties (saturation magnetic flux density ∼1.5–1.68 T, coercivity ∼41–120 Am⁻¹), and can be useful for high magnetic flux density and high frequency applications.

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(W,Ti)C and Si nanopowders were obtained using high-energy ball milling. A dense, nanostructured (W,Ti)Si₂-SiC composite was synthesized by a one-step, high-frequency induction heated combustion synthesis method within 2 min from mechanically activated powders of (W,Ti)C and 3Si. Simultaneous combustion synthesis and consolidation were accomplished under the combined effects of an induced current and mechanical pressure. The average grain size and mechanical properties of the composite were investigated.

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Nanopowders of TiCo were synthesized from Ti and Co by high energy ball milling. A highly dense nanostructured TiCo compounds were consolidated at low temperature by high-frequency induction heat sintering within 1 min of the mechanical synthesis of the powders (TiCo) and horizontal milled Ti+Co powders under 100 MPa pressure. This process allows very quick densification to near theoretical density and prohibits grain growth in nano-structured materials. The grain sizes of TiCo compounds were calculated. Finally, the average hardness values of nanostructured TiCo compounds were investigated.

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Experiments to remove non-metallic inclusions from aluminum were conducted on a laboratory-scale apparatus by electroslag refining using KCl-NaCl-Na₃AlF₆ flux. It was found that the removal efficiency of electroslag refining for alumina inclusions increases with the decrement of the remelting speed and the removal efficiency can exceed 97% under the remelting speed of 108 g·min⁻¹. The reaction of the molten slag to capture inclusions in the electroslag refining process was the main reason for the removal of inclusions. The Gibbs energy calculation of the inclusion-melt-slag system accounts for the transfer of inclusions from the aluminum melt to the molten slag thermodynamically.

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Magnetic properties and martensitic transformation response of the Ni₄₃Co₇Mn₃₉Sn₁₁ metamagnetic shape memory alloy compacts fabricated by pressureless sintering were investigated. The porous specimens sintered at 1173 K for 48 h show drastic change of electrical resistivity and magnetization due to martensitic transformation, and the features of magnetic-field-induced martensitic transformation behavior are almost the same as those in bulk specimens. In the porous specimens, the large metamagnetic shape recovery ratio over 40% was observed at 320 K with the application of 8 T magnetic field.

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The objective of this study was to investigate the cross-roll rolling process effects on microstructures and mechanical properties of AZ31 Mg sheet about rolling angle, in which the roll axes were tilted 0°, 2.5°, 5° and 7.5° away from the transverse direction. Three-dimensional FEM simulation proved that increasing the cross-roll angle, the through-thickness variation of effective strains decreases extremely. The cross-roll rolled and subsequently annealed samples have the uniform and fine grain size at whole thickness layers with increasing the cross-roll angle from 0° to 7.5°. The result of tensile test discloses that while the increase in cross-roll angle can scarcely affect on the strength of samples, it can improve the formability of samples remarkably.

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Six millimeter thick extruded ZK60 magnesium alloy plate was subjected to friction stir processing (FSP) at 400 rpm and 100 mm/min, producing fine and uniform recrystallized grains with predominant high-angle grain boundaries of 73%. Maximum elongation of 1800% was achieved at a relatively high temperature of 325°C and strain rate of 1×10⁻³ s⁻¹. Grain boundary sliding was identified to be the primary deformation mechanism in the FSP ZK60 alloy by superplastic data analyses and surface morphology observation. The superplastic deformation kinetics of the FSP ZK60 alloy was faster than that of the high-ratio differential speed rolled ZK60 alloy.

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The Ni-P coatings were deposited on closed-cell aluminum foams substrate by electroless process. Electroless coatings cover the entire surface of the foams (thickness ∼30 μm) with a high corrosion resistance (corrosion current density 15.5 μA/cm², as compared to the 308.8 μA/cm² of as-received aluminum foams).

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