MATERIALS TRANSACTIONS
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ONLINE ISSN: 1347-5320
PRINT ISSN: 1345-9678

MATERIALS TRANSACTIONS Vol. 60 (2019), No. 6

  • PREFACE

    pp. 849-849

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    DOI:10.2320/matertrans.MPR2019903

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  • Evaluation of Fatigue Crack Propagation Behavior of Pressurized Sintered Ag Nanoparticles and Its Application to Thermal Fatigue Life Prediction of Sintered Joint

    pp. 850-857

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    DOI:10.2320/matertrans.MH201802

    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.
  • Development of Polyester-Modified Epoxy Resins for Self-Organization Soldering

    pp. 858-864

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    DOI:10.2320/matertrans.MH201803

    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.
  • Effect of Specimen Size on Toughness Evaluation by Charpy Test

    pp. 865-867

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    DOI:10.2320/matertrans.MH201806

    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.
  • Measurements and FEM Analyses of Strain Distribution in Small Sn Specimens with Few Crystal Grains

    pp. 868-875

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    DOI:10.2320/matertrans.MH201808

    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.
  • Evaluation of Fatigue Crack Propagation of Sn–5.0Sb/Cu Joint Using Inelastic Strain Energy Density

    pp. 876-881

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    DOI:10.2320/matertrans.MH201813

    In this study, evaluation of fatigue crack properties in the Sn–5.0Sb/Cu joint was performed by using the inelastic strain energy density Win around the crack tip which was calculated by FEM. Win-c given by the multiplication of Win 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 ΔWin-c held. However, the power exponent in the fatigue crack propagation law differed depending on the regions of ΔWin-c. The power exponent became about 1 in the low ΔWin-c region and very large in the high ΔWin-c region. In the low ΔWin-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 ΔWin-c region and the cleavage fracture was observed. The large power exponent in the high ΔWin-c region was attributed to the cleavage fracture.
  • Tensile Behavior and Superplastic Deformation of Sn–Bi–Cu Alloy

    pp. 882-887

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    DOI:10.2320/matertrans.MH201811

    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.
  • Effects of Ni Addition to Sn–5Sb High-Temperature Lead-Free Solder on Its Microstructure and Mechanical Properties

    pp. 888-894

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    DOI:10.2320/matertrans.MH201809

    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.
  • Compound Growth due to Isothermal Annealing of Cu-Clad Al Wire

    pp. 895-901

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    DOI:10.2320/matertrans.MH201804

    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.
  • Influence of Silica Filler Addition on Fatigue Crack Propagation Rate of Underfill Resin

    pp. 902-908

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    DOI:10.2320/matertrans.MH201812

    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.
  • Effect of Bi Addition on Tensile Properties of Sn–Ag–Cu Solder at Low Temperature

    pp. 909-914

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    DOI:10.2320/matertrans.MH201807

    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.
  • Conversion of Magnetic Freedoms into Atomic Configurational Freedoms within the Cluster Variation Method

    pp. 915-920

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    DOI:10.2320/matertrans.M2018397

    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.
  • Difference in the Effect of Cold Working and Tempering on Microstructure of Mod.9Cr–1Mo Steel

    pp. 921-928

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    DOI:10.2320/matertrans.H-M2019818

    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.
  • Effect of Solidification Rate on the Microstructure and Strain-Rate-Sensitive Mechanical Behavior of AlCoCrFeNi High-Entropy Alloy Prepared by Bridgman Solidification

    pp. 929-934

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    DOI:10.2320/matertrans.M2018380

    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.
  • Representation of Nye’s Lattice Curvature Tensor by Log Angles

    pp. 935-938

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    DOI:10.2320/matertrans.M2019049

    The log angles of a rotation matrix are three independent elements of the logarithm of the rotation matrix. Nye’s lattice curvature tensor κij is discussed by using the log angles. For the change in a crystal orientation ΔR with the change in a position Δxi, it is shown that the elements of κij are written as κij = Δωixj using the log angles Δωi 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.
  • Alignments and Orientations of MnSn2 Phase during the Solidification Process of Sn–Mn Alloy under a High Magnetic Field

    pp. 939-943

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    DOI:10.2320/matertrans.M2019030

    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.
  • Influence of Minor Sc Addition on Microstructure and Mechanical Properties of Extruded Al–7Zn–2Mg–1.5Cu–0.1Zr Alloy in T6 Heat Treatment

    pp. 944-949

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    DOI:10.2320/matertrans.M2019020

    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.
  • Fatigue Property and Design Criterion of Cast Steel for Railway Bogie Frames

    pp. 950-958

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    DOI:10.2320/matertrans.Z-M2019814

    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.
  • Crystal Plasticity Analysis of Microscopic Deformation Mechanisms and GN Dislocation Accumulation Depending on Vanadium Content in β Phase of Two-Phase Ti Alloy

    pp. 959-968

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    DOI:10.2320/matertrans.M2019016

    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 (Vβ). 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 Vβ 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 Vβ. 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.
  • Effect of Friction Stir Processing on Hardness and Microstructure in La-Based Bulk Metallic Glass Composites

    pp. 969-974

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    DOI:10.2320/matertrans.M2019004

    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.
  • Creep Behavior in Pure Magnesium at Room Temperature

    pp. 975-979

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    DOI:10.2320/matertrans.M2018334

    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.
  • Simultaneous Recovery of Zinc and Manganese from Cadmium-Containing Mixed-Battery Leachate by Separation and Purification Process

    pp. 980-987

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    DOI:10.2320/matertrans.M2019033

    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.
  • Desilication of Highly Acidic Titanyl Chloride Solution for the Production of High-Purity Titania Pigment from a Spent Selective Catalytic Reduction Catalyst

    pp. 988-996

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    DOI:10.2320/matertrans.M2019045

    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 of Wrinkle in Sheet Metal Forming —Evaluation by FDTD Analysis and Ultrasonic Measurement Using Model Specimen—

    pp. 997-1003

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    DOI:10.2320/matertrans.P-M2019815

    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.
  • Measurement and Functional Approximation of Peening Intensity Distributions

    pp. 1004-1010

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    DOI:10.2320/matertrans.P-M2019816

    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.
  • Microstructures of Cemented Carbide Dipped in Molten High Chromium Cast Iron

    pp. 1011-1017

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    DOI:10.2320/matertrans.F-M2019820

    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.
  • Effect of Sintered Reinforcement on Characteristics of MWCNT-Reinforced Aluminum Alloy Composite via Friction Stir Processing

    pp. 1018-1025

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    DOI:10.2320/matertrans.M2019025

    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.
  • Optimum Temperature for HIP Bonding Invar Alloy and Stainless Steel

    pp. 1026-1033

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    DOI:10.2320/matertrans.M2018346

    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.
  • Three-Dimensional Glass Furnace Model of Combustion Space and Glass Tank with Electric Boosting

    pp. 1034-1043

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    DOI:10.2320/matertrans.M2019044

    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 on the Quality of Fluxless Mg–Nd–Zn–Zr Melt Preparation

    pp. 1044-1050

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    DOI:10.2320/matertrans.M2018364

    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.
  • High-Temperature Thermoelectric Properties of Pr1−xSrxFeO3 (0.1 ≤ x ≤ 0.7)

    pp. 1051-1060

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    DOI:10.2320/matertrans.E-M2019812

    Polycrystalline specimens of Pr1−xSrxFeO3 (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.
  • Heat Treatment Effects on Electrical Resistivity of Spinel Ferrite Layer for Powder Magnetic Core

    pp. 1061-1065

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    DOI:10.2320/matertrans.Y-M2019813

    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.
  • FeNi and Fe16N2 Magnets Prepared Using Leaching

    pp. 1066-1071

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    DOI:10.2320/matertrans.M2019019

    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.
  • Fabrication and Thermoelectric Property of Bi0.88Sb0.12/InSb Eutectic Alloy by Melt Spinning and Spark Plasma Sintering

    pp. 1072-1077

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    DOI:10.2320/matertrans.M2018383

    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.
  • Enhanced Thermoelectric Properties of Ga and Ce Double-Filled p-Type Skutterudites

    pp. 1078-1082

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    DOI:10.2320/matertrans.M2018386

    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 GaxCeFe3.5Co0.5Sb12−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 (GaVF)2x/3CeFe3.5Co0.5Sb12−x/3(GaSb)x/3, where GaVF and GaSb 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.
  • Effect on Electrochemical Properties of Phases in AB-Type Zr–Ti–Nb–Ni Alloys as Nickel-Metal Hydride Batteries

    pp. 1083-1089

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    DOI:10.2320/matertrans.MBW201807

    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 Zr0.49Ti0.5Nb0.01Ni 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 Zr0.54Ti0.47Nb0.01Ni0.98 and Zr0.47Ti0.52Nb0.01Ni, 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.
  • Solvent Extraction Separation of Silver(I) and Zinc(II) from Nitrate Leach Solution of Spent Silver Oxide Batteries with D2EHPA

    pp. 1090-1095

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    DOI:10.2320/matertrans.M2018394

    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 Processed by Selective Laser Melting

    pp. 1096-1102

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    DOI:10.2320/matertrans.M2018374

    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.

Article Access Ranking

18 Jun. (Last 30 Days)

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18 Jun. (Last 30 Days)

  1. blast furnace
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  5. inclusions
  6. a structurally-based viscosity model of the fully liquid slags in the cao-mgo-al2o3-feo-sio2 system
  7. bubbling ladle
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  9. joo hyun park
  10. mold flux, b2o3