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

MATERIALS TRANSACTIONS Vol. 58 (2017), No. 2

  • Decrease in Process Pressure for Forming Au-to-Au Joints via Reduction Reaction of Ag2O

    Taro Inoue, Tomo Ogura, Akio Hirose

    pp. 127-130

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    DOI:10.2320/matertrans.MA201602

    Abstract

    In this study, we were able to form strong Au-to-Au joints using a silver oxide (Ag2O) paste sintered at 300℃. We successfully reduced the processing pressure applied during sintering by 0.5 MPa by optimizing the sintering conditions. Through X-ray diffraction phase analysis as well as crystallite size calculations, we observed a significant reduction (27%) in the crystallite size as the heating rate was increased from 10℃/min to 180℃/min. Scanning electron microscopy cross-sectional observations confirmed that the high heating rate facilitated sintering within the bonding layer. The bonded shear strength (maximum of 24 MPa) was higher than that of the conventional Pb-5Sn solder (18 MPa), proving the suitability of Ag2O paste as a potential lead-free bonding material for high-temperature applications.

  • Resistance to Oxidation at 150℃ of Sub-Micrometer Diameter Silver-Coated Copper Particles Produced by Wet Chemical Synthesis and Immersion Plating

    Yong Moo Shin, Jong-Hyun Lee

    pp. 131-136

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    DOI:10.2320/matertrans.MA201601

    Abstract

    Sub-micrometer diameter Cu particles fabricated in air by wet synthesis at 80℃ for 2 h were immersion plated with Ag to produce an inexpensive conductive paste filler aimed at achieving fine printed patterns. Increasing the volume ratio of hydrazine hydrate to ammonium hydroxide used during wet synthesis was found to accelerate the rate of reduction and increase the yield of Cu particles to as much as 97.56% when an optimal ratio of 3:7 was used. The resulting particles (average size = 0.56 μm) exhibited excellent dispersion, with the use of an optimal Ag concentration of 15 mass% in their subsequent immersion plating producing a continuous Ag shell and a 0.62 μm average diameter. Increasing the Ag concentration beyond this, however, resulted in abrupt agglomeration between the particles, as well as the formation of cavities and spherical pure Ag particles. Those particles produced under optimal conditions experienced only a slight weight increase of 0.4% after 75 min exposure to air at 150℃, suggesting that they have an excellent resistance to oxidation at this temperature.

  • Effects of Leveler Concentration in High Aspect Ratio Via Filling in 3D SiP

    Se-Hyun Jang, Tai-Hong Yim, Young-Sik Song, Jae-Ho Lee

    pp. 137-139

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    DOI:10.2320/matertrans.MA201607

    Abstract

    3D packaging field is actively being studied in order to obtain better characteristics, such as shorter interconnection, reduction in signal delay, etc. Electroplating copper via filling is the most important technology in 3D stacking interconnection of SiP. Copper is inexpensive electrode material that has excellent electrical properties and easily obtained. In this study, the effects of leveler concentration in high aspect ratio via filling was investigated without the addition of other additives such as inhibitor and accelerator. Tetronic 701 was used as leveler. The effects of leveler on copper deposition was investigated using galvanostatic, polarization and cyclic voltammetric techniques. High overpotential of copper deposition in tetronic 701 added solution was confirmed. Finally, the optimum conditions of copper via filling in high aspect ratio via (diameter 10 μm, depth 150 μm, AR 15) was obtained.

  • Tensile Properties of Bi Alloys and a Case Study for Alloy Design in Their Application to High Temperature Solders

    Meiqi Yu, Zhefeng Xu, Yong Bum Choi, Takuma Konishi, Kazuhiro Matsugi, Jinku Yu, Satoshi Motozuka, Ken-ichiro Suetsugu

    pp. 140-147

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    DOI:10.2320/matertrans.MA201605

    Abstract

    The s-orbital energy levels (Mk) of some alloying elements in a Bi cluster model were obtained on the basis of the molecular orbital calculation. In contrast, binary Bi-Cu/-Ag/-Zn system alloys with ΔMk of 0.013–0.343 were manufactured and tension- or hardness-tested, where ΔMk was the compositional average of Mk. The ultimate tensile strength and hardness were improved as alloying elements were added and increased in alloys. There was the relation between the ultimate tensile strength, fracture strain or hardness and ΔMk. Further, the compositions of Bi-2.0Ag-0.5Cu (ΔMk: 0.180), Bi-5.0Ag-0.5Cu (ΔMk: 0.379) and Bi-0.25Cu-0.25Sb (ΔMk: 0.044) were proposed as ternary alloys. It is found that the ultimate tensile strength, fracture strain and hardness values of ternary alloys could be also able to predict using their estimation lines obtained from binary Bi system alloys.

  • Effects of Complexing Reagent on Electroless Nickel Iron Alloy Plating for the Diffusion Barrier of UBM

    Ja-Kyung Koo, Jae-Ho Lee

    pp. 148-151

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    DOI:10.2320/matertrans.MA201606

    Abstract

    Electro and electroless nickel platings have been extensively used as a diffusion barrier in under bump metallization (UBM) or as a surface finish on printed circuit boards (PCB). Even though a thin Ni layer on top of Cu can reduce the interfacial reactions with Sn-rich solders at a low reflow temperature, it may not be so effective when a reflow process is performed at a higher temperature and for a longer period. To provide a more robust diffusion barrier layer than electrodes Ni, electroless NiFe alloy system has been proposed. Since the electroless Ni-Fe plating bath has been rarely studied, the proper baths were not available commercially. In this research, the electroless plating of Ni-Fe alloys was investigated on the basis of complexing reagent. The stability of complexing reagent was studied. The compositions of electroplating layers were analyzed with EDS. The desired Ni-Fe alloy were obtained by controlling the chemical composition of the bath and its operating parameters.

  • Evolution of Carbides in H13 Steel in Heat Treatment Process

    Hao Wang, Jing Li, Cheng-Bin Shi, Ji Li, Bao He

    pp. 152-156

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    DOI:10.2320/matertrans.M2016268

    Abstract

    In the present work, the carbides in H13 steel were investigated with scanning electron microscope (SEM), energy dispersive spectrum (EDS), X-ray diffraction (XRD), and quantitative analysis method. The experimental results were compared with the calculation results by Thermo-calc software. The results show that the dendritic segregation exists generally in H13 ingots, primary M(C, N), M6(C, N) and a small amount of secondary carbides M7C3 precipitate in the segregation area. The composition segregation is improved after annealing and forging process. A large amount of secondary carbides M7C3 precipitate in the segregation area after annealing process. Primary carbide M6(C, N) are almost dissolved and M(C, N) are partially dissolved in the forged and annealed H13 steel. Most of carbides in the quenched and tempered H13 steel are fine secondary M6(C, N), M23C6 and M(C, N), besides a small amount of primary M(C, N) with smaller size. The evolution mechanism of carbides in heat treatment process was clarified by the calculated results.

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  • Infrared Spectroscopic and Computational Studies on Li4FeH6 with High Gravimetric Hydrogen Density

    Takahiro Ogata, Toyoto Sato, Shigeyuki Takagi, Hiroyuki Saitoh, Yuki Iijima, Biswajit Paik, Shin-ichi Orimo

    pp. 157-159

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    DOI:10.2320/matertrans.M2016345

    Abstract

    We report the vibrational properties of Li4FeH6 with the highest gravimetric hydrogen density in Fe-based complex hydrides. The Fourier transform infrared (FTIR) spectrum shows a broad and weak peak at 600–1000 cm−1 and an intense one at 1400–1800 cm−1, which are assigned with the aid of first-principles calculations to be the H–Fe–H bending modes, and the antisymmetric Fe–H stretching modes, respectively. From the obtained peak frequency of asymmetric stretching modes of Li4FeH6, the Fe–H bond length is estimated to be 1.6 Å, which is in good agreement with the one predicted by first-principles calculations.

  • Thermoelectric Properties of p-Type Cr Doped MnSiγ Prepared by Liquid Quenching Technique

    Swapnil Ghodke, A. Yamamoto, M. Omprakash, H. Ikuta, T. Takeuchi

    pp. 160-163

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    DOI:10.2320/matertrans.M2016246

    Abstract

    In this work, higher manganese silicide (HMS) with partial substitution of Cr for Mn has been studied. The Cr substitution was used to tune the carrier concentration for obtaining optimized thermoelectric properties. In order to have a wide range of carrier concentration, we employed liquid quenching technique, because the rapid quenching increases the solubility of Cr in HMS. The maximum solubility of 11 at.% Cr at Mn site in HMS was achieved in this study. The hole concentration increases with increasing Cr concentration, with that minimum electrical resistivity of 1 mΩcm was observed for Mn25.3Cr11Si63.9. The power factor was decreased with increasing Cr concentration due to reduction in Seebeck coefficient, but further addition of Cr showed increasing tendency for power factor. The maximum power factor of 1.5 mWm−1K−2 with ZT of 0.4 was obtained at 700 K for Mn25.3Cr11Si63.9.

  • Effect of Shot Peening on Residual Stress and Microstructure in the Deformed Layer of Inconel 625

    L.H. Wu, C.H. Jiang

    pp. 164-166

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    DOI:10.2320/matertrans.M2016298

    Abstract

    Effect of shot peening on residual stress and microstructure in the deformed layer of Inconel 625 was investigated. Residual stress and microstructure including the domain size, micro strain and dislocation density was characterized by X-Ray diffraction method (XRD). The results showed that shot peening (SP) can significantly improve the compressive residual stress and micro hardness. Moreover, microstructure evaluation revealed that smaller domains were refined and the higher micro strain was induced by shot peening process. Thus a high dislocation density in the near-surface of the deformed layers was induced. Dual shot peening process could optimize the distribution of both compressive residual stress and the microstructure, which will help with the material fatigue and corrosion resistance.

  • Extra Electron Diffraction Spots Caused by Fine Precipitates Formed at the Early Stage of Aging in Al-Mg-X (X=Si, Ge, Zn)-Cu Alloys

    Kenji Matsuda, Akihiro Kawai, Katsumi Watanabe, Seungwon Lee, Calin D. Marioara, Sigurd Wenner, Katsuhiko Nishimura, Teiichiro Matsuzaki, Norio Nunomura, Tatsuo Sato, Randi Holmestad, Susumu Ikeno

    pp. 167-175

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    DOI:10.2320/matertrans.L-M2016839

    Abstract

    Age-hardenable Al-Mg-Si, Al-Mg-Ge, and Al-Zn-Mg alloys including Cu were investigated by transmission electron microscopy to understand extra diffraction spots that appear in their selected area electron diffraction patterns. These alloys containing Cu exhibit similar extra diffracted spots to each other with diffracted spots or streaks for Al matrix and major precipitates in each alloy. The extra spots cannot be confirmed in Cu-free alloys. The initial cluster, which is based on the β''-phase in the Al-Mg-Si alloy, is proposed to be MgSi(/Ge)Mg, CuMgSi(/Ge), AlCuMg, and AlZnMg, while the second clusters, which consist of three initial clusters including anti-phase boundary short-range order, are proposed for Cu-containing alloys.

  • Grain Refinement of Aluminum Alloy Bar by a Modified RAP Process for Semi-Solid Forming

    Yongfei Wang, Shengdun Zhao, Chenyang Zhang

    pp. 176-181

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    DOI:10.2320/matertrans.M2016271

    Abstract

    A modified Recrystallization and Partial Melting (RAP) process including Radial Forging (RF) and Semi-Solid Isothermal Treatment (SSIT) was proposed to refine the grains of 6063 Al alloy bar for semi-solid forming. The 6063 Al alloy bar (φ120 mm × 800 mm) was deformed by RF into a stepped shaft with different Area Reduction Ratios (ARRs) at the temperature of 300℃, and then the samples cut from both the central and peripheral parts of the RF-deformed bar were treated with SSIT at 630℃ for 10 min. The effect of ARR on the microstructural evolution of semi-solid 6063 Al alloy was investigated. Results showed that, during the RF process, the microstructures of the samples became denser as the ARR increased. After SSIT, with the increase of ARR, the average grain sizes of both the central and peripheral parts were reduced and the spheroidization degrees of both the central and peripheral parts were improved. The variation tendency of grain size experienced three different stages: precipitous reduction, gentle reduction and unobvious change. Besides, the differences between grain sizes of the peripheral and central parts were gradually decreased with the increase of ARR. Additionally, the optimal process parameter for refining grains was 70% ARR at 630℃ for 10 min.

  • Effect of Electrodes and Post Weld Solution Annealing Treatment on Microstructures, Mechanical Properties and Corrosion Resistance of Dissimilar High Nitrogen Austenitic and Conventional Austenitic Stainless Steel Weldments

    Himanshu Vashishtha, Ravindra V. Taiwade, Sumitra Sharma

    pp. 182-185

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    DOI:10.2320/matertrans.M2016175

    Abstract

    In the present investigation, the dissimilar metal butt joints between low nickel high nitrogen 201 stainless steel and conventional 304 stainless steel were prepared by shielded metal arc welding process with two different fillers, E308L and E309L. The effects of fillers, along with variation in solution annealing temperature as 1050℃ and 1100℃, on the microstructural characteristics, mechanical properties, and intergranular corrosion behaviour of dissimilar weldments were investigated. The primary δ-ferrites of fusion zone were transformed into austenite at the solution annealing temperature for both the fillers and the transformation rate was accelerated with the increased solution annealing temperature. This led to a reduction in the ferritic-austenitic interface and subsequently improved the corrosion resistance. The double loop electrochemical potentiodynamic reactivation test was performed to measure the degree of sensitization. The fracture surface examination of weldments revealed the presence of a fibrous structure before the solution annealing treatment and demonstrated a ductile failure. After the solution annealing treatment, the ferrite to austenite transformation treatment led to a river like morphology and indicated for brittle fracture.

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  • Effects of Alloying Elements on Static Recrystallization Behavior of Work-Hardened Austenite of High Carbon Low Alloy Steel

    Manabu Kubota, Yukiko Kobayashi, Kohsaku Ushioda, Jun Takahashi

    pp. 186-195

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    DOI:10.2320/matertrans.M2016343

    Abstract

    Many studies have investigated the effect of alloying elements on the recrystallization behavior of work-hardened austenite. However, the recrystallization behavior of high carbon low alloy steel has not yet been systematically investigated. In this study, the effects of alloying elements (Al, Nb, V, Ti, and B) are examined by means of a double-hit compression test, transmission electron microscopy (TEM) observation and atom probe tomography (APT) analysis. The following conclusions were obtained:(1) When alloying elements are in solution, Nb and Ti have an equally strong effect on inhibiting recrystallization, followed by V.(2) When the deformation and holding temperature becomes low, the recrystallization is significantly inhibited by adding 0.1% V.(3) Fine particles were not observed by APT in the 0.1%V steel, which shows the strong inhibition effect on recrystallization. The solute V content measured by APT decreased as the holding time increased, and recrystallization commenced at the time when relatively coarse precipitates were formed. This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 80 (2016) 620–629.

  • Effect of Carbon Content on Static Recrystallization Behavior of Work-Hardened Austenite in Low Alloy Steel and Its Mechanism

    Manabu Kubota, Yukiko Kobayashi, Kohsaku Ushioda, Jun Takahashi

    pp. 196-205

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    DOI:10.2320/matertrans.M2016344

    Abstract

    Many studies have investigated the effect of alloying elements on the recrystallization behavior of work-hardened austenite. However, the recrystallization behavior of high carbon low alloy steel has not yet been systematically investigated. In this study, the effects of alloying elements, focusing on the carbon content, are examined by means of a double-hit compression test. The following conclusions were obtained:(1) An independent effect of carbon content on the recrystallization behavior is not recognized.(2) The effects of the Nb, Ti, and V additions on inhibiting recrystallization are amplified when the carbon content is increased from 0.1% to 0.55%.(3) The carbon content dependency of the effects of the Nb and Ti addition on recrystallization becomes weaker when the deformation and holding temperature becomes lower.(4) C–V complexes or very fine VC clusters are considered to be responsible for an inhibiting recovery and recrystallization of 0.55%C–0.1%V steel, which shows a very strong inhibition effect. This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 80 (2016) 630–639.

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  • Fabrication of Laminated Spark Plasma Sintered Compacts Composed of Alumina-Particle-Dispersed Magnesium and Magnesium

    Shigehiro Kawamori, Hiroshi Fujiwara, Yoshinori Nagai, Yukio Kasuga

    pp. 206-210

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    DOI:10.2320/matertrans.M2016289

    Abstract

    To reduce the weight of 20 vol% Al2O3-particle-dispersed Mg (Al2O3/Mg) compacts produced by spark plasma sintering (SPS), which are much harder than practical high strength AZ91 Mg alloys, 20/0/20 vol% laminated SPS compacts sandwiching a lightweight 0 vol% Al2O3/Mg (0 vol%) layer between two 20 vol% Al2O3/Mg (20 vol%) layers were fabricated by a mechanical milling/SPS process, and their microstructures and mechanical properties were investigated. The density of the 20/0/20 vol% laminated SPS compacts was 1.88 Mg·m−3, and they could be lightened to approximately 80% of the weight of equivalent 20 vol% SPS compacts. The 20/0/20 vol% laminated SPS compacts had a slightly higher hardness than the 20 vol% SPS compacts and a much higher hardness than AZ91 alloys. The bending strength of the 20/0/20 vol% laminated SPS compacts was almost the same as that of the 20 vol% SPS compacts, and was higher than the value calculated from those of the 20 and 0 vol% SPS compacts using the rule of mixtures. A new phase appeared at the flat interface between the 20 and 0 vol% layers with excellent adhesion to the adjoining layers, so this phase probably had a strong effect on the bending strength of the 20/0/20 vol% laminated SPS compacts. The new phase generated a monotonically decreasing hardness gradient from the 20 vol% layer to the 0 vol% layer and was formed by diffusion of Al and O from the 20 vol% layer and diffusion of Mg from the 0 vol% layer. The new phase most likely consisted of αMg, MgO, and Mg17Al12, and the concentrations of Al in the αMg, MgO, and Mg17Al12 components of this phase were considered to decrease from the 20 vol% layer to the 0 vol% layer.

  • Effect of pH on Hydrogen Absorption into Steel in Neutral and Alkaline Solutions

    Norihiro Fujimoto, Takashi Sawada, Eiji Tada, Atsushi Nishikata

    pp. 211-217

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    DOI:10.2320/matertrans.M2016360

    Abstract

    The corrosion behavior and the amount of absorbed hydrogen in steel were investigated in neutral and alkaline solutions with pH values ranging from 8.3 to 12.4. The amount of absorbed hydrogen into steel during immersion in the solutions was evaluated by thermal desorption analysis. In the alkaline solution of pH 12.4, the steel maintained a noble potential in a passive state, and almost no hydrogen absorption into the steel was detected. However, as the pH moved towards a more neutral pH, the corrosion potential shifted in the less noble direction, and the amount of hydrogen absorbed increased dramatically. These results indicate that the steel surface became more active in the neutral solutions, and the hydrogen evolution reaction, one of the cathodic reactions of steel corrosion, was enhanced close to the neutral pH with decreasing corrosion potential in the less noble direction. The change of the surface state from passive to active with decreasing pH accelerated the anodic dissolution of steel and made the corrosion potential less noble, resulting in the enhancement of hydrogen evolution and absorption reactions on the steel.

  • Recrystallization Texture and Shear Band Formation in Bending

    Hiroshi Kaneko, Tatsuya Morikawa, Masaki Tanaka, Hirofumi Inoue, Kenji Higashida

    pp. 218-224

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    DOI:10.2320/matertrans.M2016363

    Abstract

    The influence of texture on the shear bands and workability in bending was examined by using an age-hardened polycrystalline high concentration of Ni-Si copper alloys with various recrystallization textures. Samples with dominant the Cube orientation of {001}<100>, the RD-rotated Cube orientation of {012}<100>, the BR orientation of {362}<853>, and the R orientation of {231}<346> were employed. The formation of shear bands and the bending workability depended on the texture in the W-shape bending test, in which the bending direction was RD. The sample with a strongly developed Cube orientation showed the best bending workability. In comparison, the samples with the developed BR orientation and random orientation showed poor bending workability. The shape of the cracks generated by bending was linear, and these cracks developed in the shear bands, which were inclined at 35–40° from the surface. To elucidate the mechanism behind shear band formation, inhomogeneous deformations were investigated using the FE-SEM/EBSD method. The dependence on the crystallographic orientations was discussed using the full constraint Taylor model premising both the plane strain compression and the shear strain modes.

  • Assessment of the Electrolyte Composition in the Degree of Sensitization in AISI 347H Stainless Steel

    V. L. Cruz-Hernández, M. A. García-Rentería, R. García-Hernández, V. H. López-Morelos

    pp. 225-230

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    DOI:10.2320/matertrans.M2016272

    Abstract

    This study evaluated the suitability of the depassivator in revealing low degrees of sensitization (DOS) in samples of wrought AISI 347H austenitic stainless steel in the as-received condition and solution heat treated (SHT) at 1050℃. Assessment of the electrolyte composition was performed by the double loop electrochemical potentiokinetic reactivation (DL-EPR) test at room temperature. The electrolyte 1.0M H2SO4 + 0.50M HCl was found to be adequate for detecting low DOS. Microstructural characterization of the as-received material revealed the presence of Cr-rich carbides. These carbides were responsible of the susceptibility to IGC.

  • Microstructure of Erbium Oxide Thin Film on SUS316 Substrate with Y2O3 or CeO2 Buffer Layers Formed by MOCVD Method

    Seungwon Lee, Takayuki Shinkawa, Kenji Matsuda, Masaki Tanaka, Yoshimitsu Hishinuma, Katsuhiko Nishimura, Teruya Tanaka, Takeo Muroga, Takahiro Sato

    pp. 231-235

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    DOI:10.2320/matertrans.M2016313

    Abstract

    Er2O3 has been known the best candidate material for insulating coating for liquid metal breeding blanket system. The formation of Er2O3 layer by MOCVD method can be succeeded on SUS316 substrate with CeO2 and Y2O3 buffer layers (100 nm and 500 nm) fabricated by RF sputtering, and their microstructures have been confirmed by SEM, TEM and STEM. The surface morphology of their layers was smaller granular structure than the previous study without buffer layer. According to cross sectional TEM (X-TEM) observation, Er2O3, CeO2/Y2O3 buffer, unknown layers and SUS substrate can be confirmed. CeO2 buffer layer has a granular structure, while Y2O3 has a columnar structure. Er2O3 layer formed on each buffer layer had finer structure without buffer layer. It has been also detected that each element does not exist so much in each layer by diffusion during fabrication according to STEM-EDS and HAADF imaging.

  • Influence of Humidity on Friction Forces in Point-Contact under Small Loads

    Rongguang Wang, Shoma Furukawa, Masanobu Imakawa

    pp. 236-242

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    DOI:10.2320/matertrans.M2016371

    Abstract

    The frictional force in point-contact between a Si3N4 probe and a polished SUS304 steel surface was investigated by lateral force microscope under different press forces and relative humidity (RH). Variations in the coefficient of friction due to adsorbed water and meniscus necking between the probe and the steel surface were analyzed. At 65% RH, the coefficient of friction between the probe and the hydrophilic surface sharply decreased from 4.0 to 1.0 as vertical nominal load increased from 6 nN to 35 nN, slowly decreasing to 0.7 when the load was increased to 66 nN. At a vertical load of 14 nN, the coefficient of friction for a hydrophilic surface increased with humidity, peaking at 3.5 at an RH of 65%, but decreasing when RH increased to 80%. The change was analyzed to be due to the amount of adhered water on the surface and the formation of meniscus necking. The coefficient of friction on a hydrophobic surface with 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDS) was much lower and independent of humidity, despite the much large adhesion force occurred between probe and PFDS molecular.

  • Foaming Process and Properties of 6063 Aluminum Foams by Melt Foaming Method

    Tong Shi, Xiang Chen, Ying Cheng, Yanxiang Li

    pp. 243-248

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    DOI:10.2320/matertrans.M2016244

    Abstract

    Aluminum foams made by 6063 aluminum alloy have been prepared by melt foaming method. The uniformity of foam pores is much concerned for that homogeneous pores attribute to excellent properties. It is mainly up to the stirring intensity when adding the blowing agent into the melt, and the cooling rate of the liquid foams. In this paper, 6063 aluminum foams have been fabricated by different stirring times of TiH2 at different cooling conditions. Microstructure, cell size uniformity and compressive property of the foams have been studied. The melt which mechanically stirred for 6 minutes before foaming and the foam cooled in the air show homogenous pore structure and good mechanical property. The use of 6063 aluminum alloy offers a new raw material to prepare foams with a uniform cell size distribution as well as good mechanical property.

  • Effect of CaCO3 Foaming Agent at Formation and Stabilization of Al-Based Foams Fabricated by Powder Compact Technique

    Aleksandra V. Byakova, Svyatoslav V. Gnyloskurenko, Takashi Nakamura

    pp. 249-258

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    DOI:10.2320/matertrans.M2016314

    Abstract

    The paper presents the results obtained by in situ observation of Al-based foams formation at heating of powder compacts with calcium carbonate (CaCO3) by comparing with those prepared with conventional titanium hydride (TiH2). Foamable precursors comprising powder of either pure aluminium or AlZnMg-alloy were used for detailed investigation of foam evolution and stability. High temperature X-ray furnace was applied for in situ visualization of foam formation. It was identified that expansion and stability of foams with CaCO3 are much superior to those with TiH2. Distribution and size of solid inclusions (network of oxide remnants, particles of foaming agent, secondary reaction products, and solid oxide skin) in the cell wall materials of studied foams as well as relevant wetting data were determined to clarify the difference in foams stability. Improved stability of foams with CaCO3 is explained on the base of stabilizing models developed by Kaptay by assuming an interfacial force, the disjoining pressure, which efficiency is variable and dependent on the distribution and wetting behaviour of the clustered oxide network/solid particles in foamy melt.

  • Microstructure and Mechanical Properties of Multilayered Cu/Ti Composites Fabricated by Accumulative Roll Bonding

    S. Jiang, N. Jia, X.H. Zhou, H. Zhang, T. He, X. Zhao

    pp. 259-265

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    DOI:10.2320/matertrans.M2016307

    Abstract

    Multilayered composites composed of pure copper and titanium (Cu/Ti) have been fabricated by accumulative roll bonding (ARB). The macroscopic lamellar structures, mechanical properties and microstructures of the composites are investigated. The results show that the Cu and Ti layers are bonded well during the ARB processing. With the increasing number of ARB cycles, Ti layers start to neck, fracture and even segregate within the Cu matrix, which is attributed to the activation of shear bands that cut through the multiple metal layers. At larger ARB cycles, the distribution of small fragmentations of Ti inside the Cu matrix is more homogeneous, which is attributed to the fact that the outer surfaces of the previously processed composite are placed in the interior of the subsequent ARB stack. Tensile testing at room temperature shows that the yield strength and the ultimate strength of the composites increased mildly with the increasing ARB cycles, while the uniform elongation of the composites is retained. Microhardness tests reveal that the increase of strength in the composites during ARB mainly results from the reinforcement of the Ti layers. The mechanical behaviors of the composites can be attributed to the effect of the mixed microstructures in the both constituent metals.

  • Structural Crosstalk between Crystallographic Anisotropy in Bone Tissue and Vascular Network Analyzed with a Novel Visualization Method

    Aiko Sekita, Aira Matsugaki, Takayoshi Nakano

    pp. 266-270

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    DOI:10.2320/matertrans.M2016383

    Abstract

    Bone tissue has a highly anisotropic microstructure derived from the crystallographic orientation of apatite and the related collagen matrix alignment. Bone is also a highly vascularized tissue; intraosseous vascularization and bone formation are intimately coupled. Meanwhile, the structural relations between intraosseous vascular networks and bone microstructure are as yet unknown, partially due to technical difficulties in visualizing precise intraosseous vasculatures. The aim of this study is to develop a visualization method suitable for the structural analysis of intraosseous vascular networks and to reveal the relations between bone microstructure and the arrangement patterns of intraosseous vasculatures. Three-dimensional vascular networks were successfully visualized, and region-dependent arrangement patterns of blood vessels were clarified using fluorescent dye-conjugated lectin. Interestingly, the anisotropic structural correlation between bone matrix and the vascular system in a region-specific manner was clarified. The obtained results indicate the molecular interactions between the vascular system and bone tissue as a novel contributor for realization of anisotropic bone matrix construct.

  • Effects of Mo Addition on the Mechanical Properties and Microstructures of Ti-Mn Alloys Fabricated by Metal Injection Molding for Biomedical Applications

    Pedro Fernandes Santos, Mitsuo Niinomi, Ken Cho, Huihong Liu, Masaaki Nakai, Takayuki Narushima, Kyosuke Ueda, Yoshinori Itoh

    pp. 271-279

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    DOI:10.2320/matertrans.M2016286

    Abstract

    Ti-Mn alloys fabricated by metal injection molding (MIM) show promising performance for biomedical applications, but their low ductility (caused by high O content and the presence of pores and carbides) requires improvement. Previously, the addition of Mo to cold crucible levitation melted (CCLM) Ti-Mn alloys efficiently improved the ductility of those alloys by promoting mechanical twinning. In the present study, Mo was added to Ti-Mn alloys fabricated by MIM. Unlike fabrication by CCLM, fabrication by MIM can produce alloys with a smaller grain size, and also introduce microstructures such as pores and Ti carbides. Thus, in order to investigate how Mo addition interacts with these typical MIM features, four alloys for biomedical applications were fabricated by MIM: Ti-5Mn-3Mo (TMM-53), Ti-5Mn-4Mo (TMM-54), Ti-6Mn-3Mo (TMM-63), and Ti-6Mn-4Mo (TMM-64). Their microstructures, mechanical properties, and tensile deformation mechanisms were evaluated. Their hardness values range from 312–359 HV, and their Young's modulus values range from 84–88 GPa; both the Vickers hardness and Young's modulus show little variation among the alloys. Although the alloys show fracture features associated with a predominantly ductile fracture mode and Mo addition successfully promotes mechanical twinning in TMM-54, the elongation of these alloys is still critically low. Compared to the TMM alloys fabricated by CCLM, the TMM alloys fabricated by MIM show slightly lower hardness and Young's modulus, and comparable tensile strength, with their low elongation remaining inadequate for such applications. In particular, TMM-63 shows the best combination of mechanical properties among the present alloys, with an elongation of 4% and an ultimate tensile strength of 1145 MPa.

  • Effect of Particle Shape on the Stereological Bias of the Degree of Liberation of Biphase Particle Systems

    Takao Ueda, Tatsuya Oki, Shigeki Koyanaka

    pp. 280-286

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    DOI:10.2320/matertrans.M-M2016837

    Abstract

    It is well known that in sectional measurements of polished ore samples, the degree of liberation is overestimated by stereological bias. The stereological bias is affected by particle shape, but the effect of particle shape on the stereological bias has not been studied systematically. In this study, particles of various shapes were modeled using a geodesic grid, and the internal structures of the particles were randomly designed. The stereological bias of liberation was assessed quantitatively by comparing the computed sectional information and the original three-dimensional information. The following results were obtained: 1) the effect of aspect ratio on the stereological bias is less than 12% when comparing cases with α ranging from 1.0 to 2.0; 2) the effect of particle surface roughness on the stereological bias is smaller than 7.6% when comparing cases with surface roughness (the quotient of the surface area of the volume equivalent ellipsoid and the surface area of a particle) ranging from 0.833 to 0.996. It was also confirmed that the previously proposed stereological correction method is applicable to irregularly shaped particles because the estimation error of the degree of liberation dramatically dropped from 56.4%–64.4% without any correction to 1.16%–3.41% using the proposed method.

  • Separation of Silver (I) and Zinc(II) from Nitrate Solutions by Solvent Extraction with LIX63

    Pan-Pan Sun, Byoung-Jun Min, Sung-Tae Kim, Sung-Yong Cho

    pp. 287-290

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    DOI:10.2320/matertrans.M2016316

    Abstract

    The separation of Ag(I) and Zn(II) from nitrate solutions using 5,8-diethyl-7-hydroxy-dodecan-6-oxime (LIX63) as the extractant was investigated as a function of nitric acid (HNO3) and extractant concentrations. Selective extraction of Ag(I) over Zn(II) was achieved with LIX63 when HNO3 concentration was in the range 0.001–1 mol/dm3. Quantitative stripping of Ag(I) from loaded LIX63 was accomplished using 5 mol/dm3 of HNO3. The McCabe-Thiele diagrams for the extraction and stripping of Ag(I) with LIX63 were constructed, and the results were verified by simulated cross-current extraction and stripping experiments. Finally, Ag(I) and Zn(II) solutions of high purity (> 99.95%) were obtained.

  • Accelerated Formation of an Ultrafine-Grained Microstructure in Closed-Cell Aluminum Foam after Extrusion and Differential Speed Rolling

    W.Y. Kim, W.J. Kim, H. Utsunomiya

    pp. 291-293

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    DOI:10.2320/matertrans.L-M2016838

    Abstract

    Plastic deformation by extrusion and high-ratio differential speed rolling on closed-cell aluminum foams resulted in the formation of ultrafine grains in the densified matrix. The microstructure had an average grain size of 1.30 μm and a fraction of high angle boundaries of 0.7. Under the same processing condition, only dynamic recovery occurred in the bulk aluminum. During deformation of the foam, continuous dynamic recrystallization accelerated at the cell walls due to the occurrence of a high degree of severe plastic deformation there. The bonded interfaces created by pore closure also provided a number of sites of high angle grain boundaries, thereby contributing to the grain refinement.

  • Evaluation of Powder Layer Density for the Selective Laser Melting (SLM) Process

    Joon-Phil Choi, Gi-Hun Shin, Hak-Sung Lee, Dong-Yeol Yang, Sangsun Yang, Chang-Woo Lee, Mathieu Brochu, Ji-Hun Yu

    pp. 294-297

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    DOI:10.2320/matertrans.M2016364

    Abstract

    In selective laser melting (SLM), powder properties like size, distribution, shape, flow, and packing have effects on the process and the final parts quality, and several standards and methods are available for representing these characteristics. However, these are not enough to explain the actual packing state of the particles across the powder bed substrate. This work reports a novel method for evaluation of the powder layer density in the SLM process. The results show that the powder characteristics measured by conventional methods are not always appropriate for determining whether a powder material is suitable for SLM.

  • Pseudocapacitive Behavior of Ag3PO4 Nanospheres Prepared by a Sonochemical Process

    Chengxiang Zheng, Hua Yang, Yang Yang

    pp. 298-301

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    DOI:10.2320/matertrans.M2016312

    Abstract

    Ag3PO4 nanospheres with an average size of ～300 nm were synthesized via a sonochemical process. The electrochemical performances of the as-synthesized Ag3PO4 nanospheres in aqueous KOH electrolyte with different concentrations were investigated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The measured cyclic voltammetry curves as well as charge-discharge curves reveal a good pseudocapacitive behavior of Ag3PO4 nanospheres. In a 1 M KOH electrolyte at a current density of 0.5 mA cm−2, the specific capacitance of Ag3PO4 nanospheres is obtained to be 832 F g−1. However, Ag3PO4 nanospheres exhibit an inferior charge-discharge cycling stability, which could be due to the formation of Ag2O during the cycling process.

  • Stress-Rate Dependent Output Voltage for Fe29Co71 Magnetostrictive Fiber/Polymer Composites: Fabrication, Experimental Observation and Theoretical Prediction

    Fumio Narita, Kenichi Katabira

    pp. 302-304

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    DOI:10.2320/matertrans.M2016410

    Abstract

    The Villari effect of magnetostrictive materials, a change in magnetization due to an applied stress, is used for sensor/energy harvesting applications. In this work, magnetostrictive fiber/polymer composites are fabricated for the first time by embedding strong textured Fe–Co fibers in an epoxy matrix, and their stress-rate dependent output voltage characteristics are investigated. Compression tests are first conducted to measure the output voltage of a sample. A simple magnetomechanical coupling model of the magnetostrictive fiber/polymer composite is then established. The output voltage is predicted, and domain wall dynamics is discussed in relation to the macroscopic inverse magnetostrictive response (known as the Villari effect). The results show that the output voltage density of this novel Fe–Co fiber/polymer composite dramatically increases with increasing stress-rate and becomes larger than that of Fe-Ga alloy. Our work represents an important step forward in the development of magnetostrictive sensor and energy harvesting materials.
  • © 2017 The Japan Institute of Metals and Materials

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