Fatigue crack propagation rate of pressure-sintered Ag nanoparticles was investigated and prediction method of fatigue crack propagation using strain energy density computed by FEM was proposed. The fatigue crack propagation rate was lower than that of pressureless-sintered Ag nanoparticles around ambient temperature. At high temperature, multiple small cracks occurred ahead of a main crack and they were connected with one another and the propagation rate of the main crack increased, so that properties of fatigue crack propagation in the high temperature region were close to those of pressureless-sintered Ag nanoparticles.As the inelastic strain energy density and the length of its acquisition area were inversely proportional, the prediction of fatigue crack propagation that do not depend on the size of the area was possible by the use of the proportional constant of the relationship. The behavior of thermal fatigue crack propagation of sintered joint structure that was predicted by the derived fatigue crack propagation law was mostly in agreement with experimental behavior.

Novel underfill resins combining a thermoset epoxy resin with thermoplastic polyester resins have been developed for self-organization soldering. Polyester-modified epoxy resins, which are hybrid resins, exhibited minimal viscosity at the melting point of the Sn–58 mass%Bi solder, with the viscosity dependent on the content and molecular mass of the blended polyester resin. Because the epoxy resin was sufficiently compatible with the polyester resin in the hybrid, the curing reaction of the hybrid resin was similar to that of the epoxy resin. The chemical structure of the polyester resin was retained in the cured hybrid resin, imparting thermoplasticity to the hybrid resins cured with repeated heating. Successful self-organization soldering was achieved using the developed hybrid-resin-based solder paste.

Herein we present an experimental investigation on the toughness evaluation method for the samples of copper and aluminum, which are generally employed as electronic equipment parts, through the miniaturized version of the Charpy impact test. Overall, the resulting high reproducibility of the absorbed energy values informed by the miniaturized Charpy impact test can be witnessed; moreover, it is possible to compare the values given by the Japanese industrial standard (JIS) Charpy impact test to those given by the miniaturized Charpy impact test and correction factors were calculated accordingly.

Soldering is used to bond a semiconductor chip to a print circuit board (PCB). It is known that Sn, which is the base metal of Pb-free solder, shows remarkable crystal anisotropy. Clarifying the effect of Sn anisotropy on strain distribution is important for lifetime evaluation. The strain distribution in a micro specimen was measured under a tensile test by a digital image correlation method (DICM) with a microscope. Strain distributions were also analyzed by the finite element method with Hill’s anisotropic yield criterion and the crystal plasticity finite element analysis (CPFEA) with considering the critical resolves shear stress (CRSS) of each slip system. The deformation of the crystal structure of β-Sn depends on the size, number, and orientation of crystal grains. The CRSS was noticeably different for each slip system, and the yield stress varied with the orientation of crystal grains. Although the CPFEA without considering strain hardening was effective for predicting deformation within crystal grains, it is necessary to consider the strain hardening of crystals to predict the stress-strain curve of a micro specimen.

In this study, evaluation of fatigue crack properties in the Sn–5.0Sb/Cu joint was performed by using the inelastic strain energy density W_in around the crack tip which was calculated by FEM. W_in-c given by the multiplication of W_in obtained from an arbitrary-sized square region surrounding the crack tip by the side length of the square region – did not depend on the size of the square region and the element size. The fatigue crack propagated in the solder layer and the power law of Paris law type between its fatigue crack propagation rate and ΔW_in-c held. However, the power exponent in the fatigue crack propagation law differed depending on the regions of ΔW_in-c. The power exponent became about 1 in the low ΔW_in-c region and very large in the high ΔW_in-c region. In the low ΔW_in-c region, fatigue fracture propagated along the high angle grain boundaries formed ahead of the crack by the continuous dynamic recrystallization. On the other hand, the fracture transformed to static fracture mode in the high ΔW_in-c region and the cleavage fracture was observed. The large power exponent in the high ΔW_in-c region was attributed to the cleavage fracture.

The purpose of this study is to clarify the tensile behavior and deformation mechanism of the Sn–40Bi–0.1Cu alloy (mass%). Tensile tests of Sn–40Bi–0.1Cu were performed at temperatures of 298, 333, and 353 K and strain rates from 5.25 × 10⁻⁵ to 5.25 × 10⁻² s⁻¹. The tensile strength decreased and the elongation increased with increasing temperature and decreasing strain rate. Sn–40Bi–0.1Cu shows superplastic behavior at temperatures of >333 K and low strain rates of <5.25 × 10⁻⁴ s⁻¹. Microstructural observation after superplastic deformation of Sn–40Bi–0.1Cu showed that the primary crystal Sn grains could not deform along the axial direction of applied tension in the superplastic regime. The eutectic phase contributed to superplastic deformation. The strain rate sensitivity m for Sn–40Bi–0.1Cu was <0.3.

The purpose of the present study is to investigate the melting properties, microstructures, tensile properties and fatigue properties of Sn–5Sb–(0.05–0.50)Ni (mass%) high-temperature lead-free solders. The solidus temperature and liquidus temperature of the Sn–5Sb–Ni solders are approximately equal to those of the Sn–5Sb alloy. From the result of EPMA mapping analysis and the Sn–Sb–Ni ternary phase diagram, the Sn–5Sb–Ni solders are found to consist of β-Sn, SbSn and NiSb phases. As the amount of Ni in the Sn–5Sb–Ni solder increases, the number of NiSb phases increases and the phases are coarsened so that the 0.1% proof stress and tensile strength increase, and the elongation decreases at 25°C. In contrast, the effects of the Ni content on the tensile properties are negligible at 150°C and 200°C. The fatigue ductility exponent α of the Sn–5Sb–Ni solders is smaller than that of the Sn–5Sb solder at 25°C. At 150°C and 200°C, the α values of Sn–5Sb–0.05Ni and Sn–5Sb–0.10Ni remain small, whereas those of Sn–5Sb–0.25Ni and Sn–5Sb–0.50Ni increase. This means that the Sn–5Sb–Ni solders with 0.05–0.10 mass% Ni have superior fatigue properties to the Sn–5Sb solder in the temperature range from 25°C to 200°C.

To better understand the annealing mechanisms that occur in Cu-clad Al (CA) wire, the solid-state reactive diffusion between Cu and Al was experimentally examined by a metallographical technique. The hard CA (HCA) wire was prepared by drawing to decrease diameter from 10 mm to 1.5 mm, and then annealed at 250°C (523 K) for 3 h (10.8 ks). The annealed HCA wire is merely called the ACA wire. The HCA and ACA wires were isothermally annealed at temperatures of 150–270°C (423–543 K) for various periods of 12–960 h (43.2 ks to 3.46 Ms). Due to isothermal annealing, the intermetallic layer composed of the θ, η₂, δ, γ₁ and α₂ phases is produced at the original Cu/Al interface in both the HCA and ACA wires. The total thickness of the intermetallic layer is proportional to a power function of the annealing time. The exponent of the power function is 0.23–0.44 for the HCA wire and 0.33–0.53 for the ACA wire. Thus, boundary diffusion as well as volume diffusion contributes to the layer growth. Furthermore, the overall growth rate of the intermetallic layer is slightly greater for the HCA wire than for the ACA wire. Since the exponent is smaller for the HCA wire than for the ACA wire, the contribution of boundary diffusion is greater for the former than for the latter. The greater contribution of boundary diffusion may be the reason why the overall layer growth takes place faster in the HCA wire than in the ACA wire.

In this study, fatigue crack propagation testing on underfill resins with different filler content and finite element method (FEM) analysis were carried out to investigate the effects of filler content on fatigue crack propagation rate. The fatigue crack propagation rate of the underfill resin decreased with increasing filler content. FEM analysis clearly showed that fillers constrain the deformation of resin around them, which leads to inhibition of the amount of crack opening and a decrease in the energy release rate surrounding a crack tip. Since the amount of crack opening decreased with increasing filler content, it is conceivable that the decreased fatigue crack propagation rate can be attributed to a decrease in the amount of crack opening. The constraint on deformation of the base resin implies an increase in macroscopic static strength, and thus the resistance to fatigue crack propagation correlates with static strength.

In order to examine the effect of the Bi addition on tensile properties of Sn–Ag–Cu solder at low temperatures, stress-strain diagrams were acquired by tensile tests at 233 K using miniature size specimens. Stress drops were observed in the stress-strain diagram of Sn–Ag–Cu–Bi solder before it lead to a break. Similar phenomenon did not observed in the Sn–Ag–Cu solder. The stress drops was exceptionally sharp in the Sn–Ag–Cu solder with added 3 mass% Bi, compared to the solder with added 1 or 2 mass% Bi. The mode of the stress drop is depended on twin deformation. On the contrary, similar stress drop phenomenon was not observed in any stress-strain diagrams at 298 K. From the results of grain map analysis, it was found that many twin deformations occur in the specimen in which exceptional sharp stress drops appear in the stress-strain diagram.

The continuous displacement cluster variation method (CDCVM) has introduced local atomic displacements into the theoretical framework of the cluster variation method (CVM) by viewing an atom displaced from a Bravais lattice point as a particular atomic species located at the lattice point. This idea of conversion from a freedom of local displacements into configurational freedom is extended in this paper to magnetic freedoms. Various magnitudes of local magnetic moments are considered as well as two spin directions, up and down. The approach is applied to pure Ni and its Curie temperature is explored with the entropy formula of the tetrahedron approximation in the CVM using the first-nearest-neighbor pair interaction energies extracted from the total energies of various spin configurations, which are estimated from electronic-structure calculations.

The difference in the effect of cold working and tempering on the microstructure of Mod.9Cr–1Mo steel was investigated by means of X-ray diffraction (XRD), electron channeling contrast image (ECCI) and electron backscatter diffraction (EBSD) technique. For simulating the cold working, interrupted tensile tests were conducted at room temperature to prepare some specimens with 0–20% strain. Tempering was conducted at 700–760°C for 0.25–6 h in order to make heat-treated specimens with the same hardness level as interrupted tensile specimens.XRD was carried out to evaluate dislocation density. ECCI and EBSD technique were employed to evaluate lath width, inter-particle spacing and high-angle grain boundary spacing such as block and packet boundary, respectively.In the pre-strained and the tempered materials, lath width, inter-particle spacing and dislocation spacing are different despite almost the same hardness. It was found that the dislocation substructure is completely different in the pre-strained and the tempered materials. This Paper was Originally Published in Japanese in J. Jpn. Soc. Heat Treat. 57 (2017) 343–350.

AlCoCrFeNi high-entropy alloys (HEAs) were prepared by Bridgman solidification with different solidification rates, and the mechanical behavior of the HEAs was investigated over a wide strain rate range (∼10⁻³∼10³ s⁻¹). Microstructure observations suggest that, with increasing solidification rate, the microstructure evolves from coarse columnar grains to fine equiaxed ones. Through compression tests under both quasi-static and dynamic strain rates, the AlCoCrFeNi HEAs were found to possess positive strain-rate sensitivity (SRS), and the HEA with lower solidification rate exhibits higher SRS, which are attributed to the coarse grain size.

The log angles of a rotation matrix are three independent elements of the logarithm of the rotation matrix. Nye’s lattice curvature tensor κ_ij is discussed by using the log angles. For the change in a crystal orientation ΔR with the change in a position Δx_i, it is shown that the elements of κ_ij are written as κ_ij = Δω_i/Δx_j using the log angles Δω_i of ΔR. The log angles for the crystal rotation given by the axis/angle pair are also discussed. This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 82 (2018) 415–418.

It has been reported that MnSn₂ exhibited unusual magnetic behaviors related to its crystal structure. However, little work has been done to investigate its behavioral responses to a high magnetic field (HMF), which is of potentially fundamental interest. Based on this, binary Sn–Mn alloy was solidified under different HMFs in this work. The results show that the primary MnSn₂ crystals appear block- or bar-like shapes in both the longitudinal and transverse sections. In the longitudinal sections, however, the HMFs tend to align the bar-like crystals with the long axes perpendicular to the magnetic field. In the transverse sections, the HMFs have little influence on the alignments of the bar-like crystals but increase their amount. A crystallographic study indicates that 〈110〉 is the easy magnetization axis of the MnSn₂ crystals that orients preferentially parallel to the magnetic field. These results are attributed to the magnetic anisotropy of the MnSn₂ crystals.

The effects of minor Sc on microstructure and mechanical properties of Al–7Zn–2Mg–1.5Cu–0.1Zr alloy under different aging time were investigated by means of tensile test, scanning electron microscopy and transmission electron microscopy, respectively. The results show that the aging strengthening tendency of Al–7Zn–2Mg–1.5Cu–0.1Zr(–0.2Sc) alloys exhibits the similar feature. After T6 treatment, the maximum values of ultimate tensile strength and yield strength are 700 MPa and 602 MPa, respectively. The tensile fracture of Al–7Zn–2Mg–1.5Cu–0.1Zr(–0.2Sc) alloys exhibits a mixed ductile-brittle fracture. The results of TEM observation show that large amounts of GP zones and η′ phase distribute homogeneously inside the grains, and some rod-like precipitates distribute along grain boundaries in two alloys. Besides, there also exist lots of Al₃(Sc, Zr) phase in Al–7Zn–2Mg–1.5Cu–0.1Zr–0.2Sc alloy with different treated states. The grain refinement strengthening and precipitation strengthening play the dominant role in the strength increase of the Al–7Zn–2Mg–1.5Cu–0.1Zr–0.2Sc alloy.

The fatigue design criterion for members of cast steel is not specified in the design standard of railway bogie frames in Japan. The objectives of the present study involve clarifying the fatigue property of cast steel used in railway bogie frames and proposing a fatigue design criterion for members of cast steel. Fatigue tests are conducted on test specimens with casting or machined surfaces under axial loading or plane bending. The results indicate that the fatigue strength of specimens with casting surfaces exceeds that of specimens with machined surfaces. The fatigue strength under plane bending significantly exceeds that under axial loading. The results are attributed to differences in the locations and geometries of cast defects where cracks originate. A fatigue design criterion for members of cast steel is proposed by the statistical evaluation of fatigue data. Furthermore, the validity of the proposed criterion is demonstrated via a full-scale fatigue test of bogie frames with members of cast steel. This Paper was Originally Published in Japanese in J. Soc. Mater. Sci., Japan 67 (2018) 1065–1072.

Inhomogeneous deformation of a single α-β colony in a Ti–6Al–4V alloy under uniaxial tensile conditions was numerically simulated using a crystal plasticity finite element (CPFE) method, and we predicted density changes in geometrically necessary dislocations (GNDs) depending on the vanadium concentration in the β phase (V_β). The geometric model for the CPFE analysis was obtained by converting data from electron back-scatter diffraction patterns into data for the geometric model for CPFE analysis, using a data conversion procedure previously developed by the authors. The results of the image-based crystal plasticity analysis indicated that smaller V_β induced greater stress in the α phase and smaller stress in the β phase close to the α-β interfaces in the initial stages of deformation because of the elastically softer β phase with lower V_β. This resulted in greater strain gradients and greater GND density close to the interfaces in the initial stages of deformation within the single α-β colony when the β phase plastically does not deform.

Friction stir processing (FSP) was conducted on a 2.5 mm thick La₆₆Al₁₄Cu₂₀ bulk metallic glass composites (BMGCs) plate. Effects of FSP on the BMGCs have been investigated. Microstructural observations indicated that the crystalline particles were elongated and parallel to the rotating direction of the pin after FSP. Micro-hardness measurement showed that hardness of the stirred zone drops down approximately 50 Hv compared with the as-cast sample. The mechanical properties of the amorphous matrix before and after FSP have been investigated using nanoindentation test. Results shown that creep displacement-time curves of the BMGCs before and after FSP can be accurately fitted by the generalized Kelvin model which was usually used in polymeric materials. The creep compliance and creep retardation spectrum shown that the as-cast specimen is in a more relaxed state.

Grain refinement is an effective technique to increase the ductility of magnesium (Mg) at room temperature: it engenders higher minimum creep rate and large rupture strain of >170% in the sample with grain size (d) of 1.2 µm. Its creep brings about dislocation absorption and nucleation at grain boundaries, enhancing grain boundary sliding with low apparent activation energy of 65 kJ/mol, which is only 70% of that of grain boundary diffusion. Therefore, grain boundary deformation enhances ductility of Mg at the low homologous temperature of about 0.3. However, a sample with d = 6.1 µm shows low fracture strain that is only one-third of that in the fine-grained sample. Creep resistance increases with increasing grain size, meaning that grain refinement leads to good ductility but low creep resistance at room temperature.

A study on the simultaneous separation of Zn and Mn from a feed solution containing various types of dissolved battery wastes was carried out by a solvent extraction process using D2EHPA. The selective recovery of Zn and Mn from feed solutions containing Cd ions is difficult due to their similar physicochemical behavior. Therefore, 99.9% of Zn, 99.8% of Mn, and 99.9% of Cd were extracted using the optimum conditions of 40 vol% D2EHPA, 40 vol% NaOH concentration, 2-stage countercurrent extraction, and an O/A ratio of 2. The Co-extracted Co could be scrubbed using pH 2 sulfuric acid at an O/A ratio of 1, and Cd was then scrubbed using 0.5 M Na₂S₂O₃. The results of the Cd scrubbing experiments indicated that the optimum conditions were 3-stage countercurrent scrubbing and an O/A ratio of 2, and the scrubbing efficiency of Cd was approximately 99.9%. The Zn and Mn that remained in the loaded organic could be enriched by increasing the O/A ratio of the stripping stage to 6. From this concentrated solution, high purity zinc manganese sulfate powder, which can be used as a raw material for fertilizer for crop cultivation, was manufactured.

An effective desilication method for a titanyl chloride (TiOCl₂) solution obtained by dissolving sodium titanate using concentrated hydrochloric acid was investigated in order to increase the purity of titania pigment and the productivity of the process. When the TiOCl₂ solution obtained by HCl leaching was used without desilication, clogging of the filtration system or precipitation of silica occurs. To overcome these disadvantages using a simple and efficient desilication method, the acidity, preservation temperature, and time elapsed after the preservation of TiOCl₂ solution were controlled. In the experiments, TiOCl₂ solutions produced using 5–7 M HCl solution were preserved at 274–313 K for 5 days. When the acidity, preservation temperature, and time elapsed after preservation were increased, the removal efficiency of silica increased. The conditions for the concentration of silica below 1 mg/L and the removal of silica by gelation were determined. When the purified TiOCl₂ solution was hydrolyzed at 363 K, titanium dioxide with a purity of 99.6–99.9% was obtained. Therefore, the results of this study demonstrated a straightforward and effective desilication method for highly acidic TiOCl₂ solution.

Ultrasonic reflection characteristics that vary with wrinkling enable the detection of wrinkles during press forming. In this study, we investigated the influence of wrinkles on ultrasonic reflection characteristics by Finite-Difference Time-Domain (FDTD) analysis and experiments with model specimens. The wrinkle shape on the model specimen was made into a trapezoid by electric discharge machining. FDTD analysis was performed using the analysis model that reproduces experimental situations. The first reflection wave occurring at the lower surface of the upper die affected the ultrasonic characteristics, which changed with wrinkle wavelength. The effective diameter of the ultrasonic probe and the irradiation diameter of the ultrasonic wave also affected the ultrasonic reflection characteristics. In the region where the ratio of the irradiation diameter of the ultrasonic wave to the wrinkle wavelength is 0.3 or more, the reflection intensity depends on the irradiation position of the ultrasonic wave. The irradiation position at the maximum reflection intensity varies depending on the fraction of the effective diameter of the ultrasonic probe and the wrinkle wavelength. This Paper was Originally Published in Japanese in the J. JSTP 59 (2018) 47–52.

In the case of large components, shot peening is generally performed by moving peening equipment that follows a trajectory on the component surface using a robot. In this study, we aimed to obtain a functional approximation of the intensity (arc height of the Almen strip) distributions in the shot stream. The intensity distributions using various peening time and standoff distances were measured under two different experimental conditions. The measured intensity distributions were approximated by modified Gaussian distribution functions, which included the saturation curve. Three coefficients in the functions depended on the peening time and the standoff distance. For tilted shot peening, the intensity distributions were more complex because the standoff distance at each Almen strip was different. The intensity distributions of the tilted plates calculated by the modified Gaussian distribution function, which considered the variation in the standoff distance, were in good agreement with the experimental results. The intensity distributions of twice-shot peening differ from those of once-shot peening because the second peening area overlap with the first peening area. The modified Gaussian distribution function and the saturation function were used to determine the intensity distribution of a twice-shot peened sample. These calculated values were in good agreement with the experimental results. This Paper was Originally Published in Japanese in J. JSTP 59 (2018) 165–170.

High chromium cast irons show superior abrasion resistance due to their chromium carbides. Their abrasion resistance is improved by insert casting with cemented carbide. The effects of high-temperature exposure during insert casting on the microstructures of cemented carbide were investigated in this research. The high chromium cast iron (2.7%C–27%Cr) and the cemented carbide round bars (WC–13.7%Co) were prepared. The round bars were dipped in molten high chromium cast iron at 1596 K. The dipped round bars were pulled up after the elapse of 30–180 s. Microstructures of dipped round bars were changed from homogeneous sinter structure to three-layer structure, cemented carbide, diffusion layer, and reaction layer. The thicknesses of the diffusion layer and the reaction layer were increased with increasing of dipping time. FE-EPMA analysis revealed that the diffusion layer was formed by the elution of Co from the cemented carbide and diffusion of Fe and Cr from the molten high chromium cast iron into the cemented carbide round bar. In addition, rectangular particles were randomly distributed in the diffusion layer. The equivalent circular diameter of the rectangular particle was increased with increasing dipping time. The Vickers hardness of the diffusion layer decreased about 30% relative to the cemented carbide but higher than that of high chromium cast irons. The inserted cemented carbide is thought to have contributed to improving abrasion resistance. It was suggested that thin diffusion layers are more effective for improving abrasion resistance. This Paper was Originally Published in Japanese in J. JFS 90 (2018) 217–223. The abstract, background, experimental procedures, results and discussion have been revised.

In order to enhance the strength of 5083 Al alloy, fabrication of multi-walled carbon nanotubes (MWCNTs) reinforced 5083 Al alloy by the use of friction stir processing (FSP) was investigated. The MWCNT-reinforced Al alloy composites using sintered sheets of 5083 Al alloy-8%MWCNT were successfully fabricated. Grain refinement and many minute aluminum carbides (Al₄C₃) were observed in the composites fabricated. The proof stress of the composites fabricated with the 550°C sintered sheets considerably increased by 153 percent and the tensile strength increased by 55 percent compared with that of the base material.

The structure of the target vessel for the spallation neutron source will be modified. The Invar alloy which has a low coefficient of thermal expansion has to be reinforced by enclosing it completely in stainless steel using hot isostatic pressing bonding to reduce the thermal deformation of the additional flange. We examined the optimum temperature conditions for HIP bonding the Invar alloy and 316L stainless steel. The metallographic observation and mechanical tests on specimens bonded at 700°C, 900°C, 1100°C and 1200°C were conducted. The experimental results showed that the bonding region increased when the bonding temperature increased, but the tensile strength reduced when the bonding temperatures increased. The tensile strength of a specimen bonded at 1200°C was approximately 10% lower than that of the Invar bulk. From the residual stress analysis using the ABAQUS code, the tensile stress near the bonding region of the specimen bonded at 700°C was found to be 84 MPa; this stress increased with the bonding temperature up to 90 MPa. From these results, it is concluded that the optimum temperature for bonding temperature was 900°C.

The integrated glass furnace model of combustion space and glass tank is established to study the 600 t/d float glass furnaces with and without electric boosting system. In the electric boosting furnace, the electrodes are vertically installed near hot spot, and the electric power is applied to replace part of fuel supply. The temperature and velocity fields as well as glass trajectories are presented to investigate the influence of electric boosting on the glass furnace. The residence time, melting factor and mixing factor are employed to evaluate the glass quality and melting efficiency. With the electric boosting system, the crown and flame temperature at flame covering zone are lower than the temperature in furnace without electric boosting, which would prolong the lifetime of glass furnace. However, the increased temperature at batch melting zone and fining zone are induced with the increased bottom temperature. Moreover, the glass flow at glass tank is promoted with electric boosting, especially around spring zone. The average melting efficiency and glass melting quality are improved with the electric boosting system, while the melting quality of fastest particles in electric boosting case would be poorer. Additionally, the homogenization of glass melt is improved with electric boosting. With the optimum design of electric boosting system, the better glass melting quality, more homogenization, and higher melting efficiency would be achieved.

The effects of settling time up to 8 h on the quality of fluxless Mg–Nd–Zn–Zr melt preparation are discussed in terms of melt chemistry and inclusions’ structural properties. The content of Nd, Zn and Zr lie in the demanding scope throughout settling process. Neodymium content rises slightly at the settling time of 0.25 h, then decreases gradually up to 8 h. Zinc experiences a slight increase after 0.25 h, then levels off. Zirconium drops sharply at 0.25 h mainly due to the subsidence of undissolved zirconium (Zr) particles, then drops slightly at 1 h, and then stabilizes. The inclusions have various morphologies like rod-like, granular and clustered, and different types such as oxides, carbides, undissolved Zr particles, and etc. The effect of settling time on inclusions’ removal is remarkable during early settling stage, from 0 to 0.25 h, and is getting less stark with increasing time. The area fraction, average diameter and maximum diameter of inclusions all decrease rapidly at 0.25 h, then gradually, and finally reach a plateau region. The changes of minimum diameter and number density values are insignificant through whole process. The theoretical analysis on inclusions’ settling and rising behavior agrees with the experimental data.

Polycrystalline specimens of Pr_1−xSr_xFeO₃ (0.1 ≤ x ≤ 0.7) were synthesized using a solid state reaction method. All samples had a typical perovskite structure, where the orthorhombic (Pbnm) phase was dominant at x ≤ 0.5 and the rhombohedral (R-3c) phase was dominant at x ≥ 0.6. Since the B site is in the mixed valence state of Fe³⁺/Fe⁴⁺ and the spin quantum number is in the range of 0.86 ≤ s ≤ 1.15, it is expected that Fe³⁺ is in the spin state of low spin (LS) Fe³⁺ or intermediate spin (IS) Fe³⁺ and Fe⁴⁺ is in the spin state of LS Fe⁴⁺. As x increases, the ratio of IS Fe³⁺ decreases compared to that of LS Fe³⁺ at x ≥ 0.3, so that the P-type Seebeck coefficient is maintained up to x = 0.5. Although ZT = 0.002 (T = 850 K) of x = 0.7 which shows the maximum N-type thermoelectric characteristic is about 8% of ZT = 0.024 (T = 850 K) of x = 0.1 which shows the maximum P-type thermoelectric characteristic, both are the results of relatively high Seebeck coefficient, low electrical resistivity, and low thermal conductivity. Therefore, we strongly suggest that there is a possibility of application of PN elements which compose of the perovskite-type oxides. This Paper was Originally Published in Japanese in J. Thermoelec. Soc. Jpn. 15 (2018) 3–13.

The powder magnetic core having a spinel ferrite insulating layer has enabled high magnetic flux density and high electrical resistivity, because spinel ferrite exhibits magnetic insulating properties. However, its the electrical resistivity of the powder magnetic core was reduced after annealing at 873 K, since FeO was formed in the spinel ferrite insulating layer. The eutectoid transformation caused the decomposition of FeO, which decompose into Fe₃O₄ and α-Fe at the temperature range below 833 K. We verified the possibility of eutectoid transformation of FeO in the insulating layer by the two-step heat treatment at 873 K and 773 K. The presented results clearly showed that the two-step heat treatment increases the electrical resistivity of the insulating layer due to the disappearance of FeO by eutectoid transformation even in the insulating layer. This Paper was Originally Published in Japanese in J. Jpn. Soc. Powder Powder Metallurgy 65 (2018) 171–175.

L1₀-type FeNi alloys and α′′-Fe₁₆N₂ are candidates for permanent magnets without precious metals, but they are difficult to prepare because atomic diffusion is extremely slow below the order–disorder transition temperature of L1₀-FeNi (320°C) and because α′′-Fe₁₆N₂ is a metastable phase. Here, we report trials for preparing them using leaching, which is a method to obtain porous metals with a high surface area. We used such chemically active porous alloys as precursors for preparing L1₀-FeNi using the driving force of atomic diffusion and for preparing α′′-Fe₁₆N₂ using high reactivity with ammonia. No proofs for obtaining the L1₀-FeNi phase were observed, likely due to an Al impurity of 10 mol% and/or too small of a grain size. An Fe₁₆N₂ with α′′ phase was obtained. Although the saturation magnetization was smaller than that of Fe, a large coercivity (up to 121 kA m⁻¹) was obtained.

In the present study, self-assembled submicrometer-sized composite structure of bismuth-antimony (Bi–Sb) alloy and indium antimonide (InSb) were fabricated by melt-spinning (MS) technique and spark plasma sintered (SPS) process with the eutectic composition. The power factor reached 2.6 mW/mK² at 300 K. The thermal conductivity decreased by 35% compared with the Bi–Sb alloy. The results suggest that this MS-SPS procedure is promising for reducing the thermal conductivity with maintaining the electrical properties.

Among the p-type filled skutterudites, Ce single-filled (Co,Fe)Sb₃ is known as a promising thermoelectric material. Here, we try to enhance the thermoelectric properties of Ce-filled (Co,Fe)Sb₃ by co-filling of Ga. We synthesize the samples in the nominal compositions Ga_xCeFe_3.5Co_0.5Sb_12−x/3 (x = 0.06, 0.09, 0.15, and 0.21) and examined their thermoelectric properties from room temperature to 773 K. It is confirmed that Ga can occupy not only the void site but also the Sb site, i.e., the chemical formula can be expressed as (Ga_VF)_2x/3CeFe_3.5Co_0.5Sb_12−x/3(Ga_Sb)_x/3, where Ga_VF and Ga_Sb mean Ga in the void and Sb sites, respectively. Ga contributes to optimize the carrier concentration as well as to reduce the lattice thermal conductivity. Owing to these Ga contributions, the material’s thermoelectric figure of merit zT is enhanced and reaches 0.85 in maximum at 773 K, which is obtained for the sample with x = 0.15.

AB-type Zr–Ti–Nb–Ni alloys are good candidates as the negative electrode for Ni-metal hydride (MH) batteries because they have high discharge capacity around 330 mAh g⁻¹ at 303 K. The Zr_0.49Ti_0.5Nb_0.01Ni alloy consists of two phases, the primary-phase with B33-type orthorhombic structure and the secondary-phase with B2-type cubic structure. To compare electrochemical properties of each phase with the mother alloy, we synthesized the primary-phase and secondary phase alloys with compositions of Zr_0.54Ti_0.47Nb_0.01Ni_0.98 and Zr_0.47Ti_0.52Nb_0.01Ni, respectively. The discharge capacity was examined at 25 mA g⁻¹ and 303 K, showing that the primary-phase alloy has the highest value of 362 mAh g⁻¹ than the mother alloy (335 mAh g⁻¹) and the secondary-phase alloy (253 mAh g⁻¹). For cycle performance, all alloys were excellent (≧95%) at 100 mA g⁻¹ and 303 K. For high-rate dischargeability, the secondary-phase alloy was the best, probably because the stability of hydride for the secondary-phase alloy was lower than that for the mother and the primary-phase alloy.

In this study, separation of silver(I) and zinc(II) from nitrate leach solution of spent silver oxide batteries were carried out by extraction and selective stripping. Di-(2-ethylhexyl) phosphoric acid (D2EHPA) was used to extract Zn(II) and Ag(I) in the equilibrium pH range of 0.99–1.34. The extraction of Zn(II) was more affected by the pH value than that of Ag(I). Zn(II) and Ag(I) loaded in D2EHPA was separated by selective stripping with a mixture of 0.01 mol/dm³ nitric acid and 1 mol/dm³ thiourea and 0.5 mol/dm³ nitric acid for Ag(I) and Zn(II), sequentially. A process flowsheet for the separation and recovery of Zn(II) and Ag(I) from the nitrate leach solution of spent silver oxide batteries was proposed.

Novel ferritic stainless steel with advanced mechanical properties and significant magnetic responses was prepared by a selective laser melting (SLM) process from UNS S32707 hyper-duplex stainless steel (HDSS) powder prepared by a plasma rotating electrode process (PREP). The microstructure, mechanical properties, and soft magnetic properties of the sintered state were studied. The results show that ferritic stainless steel with a relative density of 98.2% (with the theoretical density of 7.8 g/cm³) can be prepared by SLM with a laser energy density of 87.96 J/mm³ and 67° of rotation of the upper and lower layers. The rapid cooling after sintering inhibits the formation of austenite, and the ferrite content reaches 98.5%. Sintered parts prepared by SLM have excellent mechanical properties. The measured tensile strength, yield strength, and the microhardness were 1493 MPa, 1391 MPa, and 528.7 HV, respectively. The nitrogen content decreased by 33% during SLM. Nitrides precipitated at ferrite grain boundaries lower the ductility and toughness of sintered parts prepared by SLM. The measured elongation, the reduction of area, and the impact absorbing energy were 13.2%, 24.1%, and 18 J, respectively. The high ferrite content causes sintered parts prepared by SLM to have excellent soft magnetic properties. The specific saturation magnetization and the coercivity were 106 Am²/kg and 1.79 mT, respectively. This provided a new approach for the near net shaping of structural and functional integrated soft magnetic materials with both strength and corrosion resistance.