Journal of the Japan Institute of Metals and Materials
Online ISSN : 1880-6880
Print ISSN : 0021-4876
ISSN-L : 0021-4876
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Volume 75, Issue 12
Displaying 1-9 of 9 articles from this issue
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Regular Articles
  • Infiltration of Light Metals into Stainless Steel Preforms Fabricated by Indirect Selective Laser Sintering
    Atsushi Yamaguchi, Kohji Gotoh, Tomoki Tomita, Shinji Fukumoto
    Article type: Regular Article
    2011 Volume 75 Issue 12 Pages 651-656
    Published: 2011
    Released on J-STAGE: December 01, 2011
    DOIhttps://doi.org/10.2320/jinstmet.75.651
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      In this study, we attempted to infiltrate molten aluminum, magnesium, and magnesium-zinc alloy into stainless steel preforms fabricated by indirect selective laser sintering (SLS). In the case of aluminum, infiltration did not occur; it was inhibited by the intermetallic compound (Al3Fe) formed by the active reaction between molten aluminum and stainless steel powder. Molten magnesium and magnesium-zinc alloy, however, smoothly infiltrated into the stainless steel preforms, and the infiltrated parts were found to maintain excellent dimensional accuracy. The hardness and tensile strength of the infiltrated parts of magnesium are 65 HRB and 265 MPa, respectively, and the corresponding values for magnesium-zinc alloy are 72 HRB and 305 MPa, respectively. The tensile strengths of the infiltrated parts are significantly higher than those of the casting materials (106 MPa for magnesium and 270 MPa for magnesium-zinc alloy). We believe that the large increase in tensile strength after infiltration was due to the composite reinforcement of the matrix and stainless steel particles. Thus, the infiltration of magnesium and magnesium-zinc alloy into stainless steel powder preform can be considered as an effective indirect SLS technique for producing lightweight infiltrated metal-alloy parts.
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  • Determination of Physical Properties for Point Defects during CZ Silicon Crystal Growth by High-Precision Thermal Simulations
    Manabu Nishimoto, Kozo Nakamura, Masataka Hourai, Toshiaki Ono, Wataru ...
    Article type: Regular Article
    2011 Volume 75 Issue 12 Pages 657-664
    Published: 2011
    Released on J-STAGE: December 01, 2011
    DOIhttps://doi.org/10.2320/jinstmet.75.657
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      The physical properties of point defects in Si crystal have not been established with certainty. That makes it difficult to calculate the behavior of grown-in defects in CZ Si crystal growth. With high-precision thermal analysis we studied the physical properties of point defects from which the grown-in defects distribution could be calculated. In this study we focused the attention on the V-I boundary in which the vacancy and self interstitial concentrations are balanced, which appears in case of slowly decreasing the crystal growth rate. we assumed that the determination of the physical properties was an optimization problem, and we applied a genetic algorithm method and a simulated annealing method. In addition, we examined the optimized physical properties with physical considerations and reproducibility of V-I boundary shape in calculation. As a result, we estimated one promising set of the physical properties, which were used to calculate the grown-in defect distribution. The calculation result showed that (1) it could reproduce the experimental results and (2) the concentration difference (ΔC) between vacancy and self interstitial was related to grown-in defect types.
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  • Fabrication of Porous Glass Supporting Silver Ultrafine Particles after Hydrothermal Treatment and Microwave Heating
    Takeshi Yoshikawa, Kei Kasamatsu, Takafumi Kanata, Nobumitsu Hirai, To ...
    Article type: Regular Article
    2011 Volume 75 Issue 12 Pages 665-670
    Published: 2011
    Released on J-STAGE: December 01, 2011
    DOIhttps://doi.org/10.2320/jinstmet.75.665
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      Fabrication of the porous glass supporting silver ultrafine particles was conducted by means of hydrothermal treatment and microwave heating. Ag2O-added glass containing water was first prepared under the hydrothermal condition of controlled water vapor pressure at 160℃. The glass containing water was then subjected to microwave heating and was changed to porous glass after foaming. The porous glass supported silver particles under 20 nm at its pore surface and showed the catalytic effect on the reaction in the aqueous solution. Accordingly, microwave heating of the glass containing water was found to be an effective process to fabricate the porous glass catalysts.
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  • Binary Solid Solution of C60-C70 Prepared by Liquid-Liquid Interfacial Precipitation Method
    Yuki Ujihara, Yutaka Takahashi
    Article type: Regular Article
    2011 Volume 75 Issue 12 Pages 671-677
    Published: 2011
    Released on J-STAGE: December 01, 2011
    DOIhttps://doi.org/10.2320/jinstmet.75.671
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      The liquid-liquid interfacial precipitation method was employed to prepare (C60)1−x(C70)x solids having good crystallinity. In reference to the case of pure C60 (Y. Takahashi et al.: J. Japan Inst. Metals 68(2004) 326), toluene and methyl alcohol were used as good and poor solvents, respectively. Under ambient pressure, the solids were successfully formed up to x=0.09, but failed to form at x≧0.10 because a (C60)1−x(C70)x•C6H5CH3 solvate was included. However, under a high pressure argon atmosphere, formation of the solvate was highly suppressed and only (C60)1−x(C70)x solids were obtained for all x when P≧4 MPa. Electron probe microanalysis identified the presence of argon in the solid. Thus it is likely that incorporation of argon atoms in the solid during precipitation disturbs solvate formation. The argon atoms were removed by heat-treatment in a vacuum at 300℃, providing pure C60-C70 solids.
       The specimens were measured by X-ray diffraction to clarify the miscibility gap between the C60-rich phase and the C70-rich phase. The former solubility limit was evaluated to be x=0.09, while the latter was in the range of x=0.8-0.9. From the x-dependence of the lattice parameter in the C60-rich phase, the partial molar volume of dissolved C70 was estimated to be smaller than that of pure C70 by only 2.6%. The system can be modeled by hard-contact mixing of two different spheres. A large tensile distortion exists in the C60 matrix in the vicinity of a C70 molecule along with an accompanying strain energy. This acts as the driving force of phase separation in the system.
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  • Effect of B Contents in Fused Salt Bath on Boriding of SUS304 Stainless Steel
    Shinji Koyama, Masashi Takada, Kentaro Kawasumi, Tatsuya Fukuda, Ikuo ...
    Article type: Regular Article
    2011 Volume 75 Issue 12 Pages 678-683
    Published: 2011
    Released on J-STAGE: December 01, 2011
    DOIhttps://doi.org/10.2320/jinstmet.75.678
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      The steel material is used for various applications, and there are a lot of parts to which wear resistance is required. For instance, steel is used in gears and turbine braid exposed to high-speed fluid which contains fine particle. The austenitic stainless steel is excellent in corrosion resistance. However, because it is not possible to stiffen by quenching, the development of the method of improving abrasion resistance is required. Recently, boriding is seen as a solution. Boriding is divided roughly into molten salt bath method, powder-pack method, gas phase method, and electrolytic method. Among the method mentioned, molten salt bath method is the easiest technique which can be processed without special equipment. In this research, the influence of the B density in molten borax on the formation layer of SUS304 steel surface was examined. Boriding were performed in molten borax which contained 1~7 mass%B at 1200 K for 14.4 ks. As a result of the examination, the surface hardness becomes about 2200 HV when the density in molten borax is 2 mass%B or more. Also the wear resistance too has improved remarkably. Furthermore, it was understood that the formation layer on the surface was FeB, and, additionally, consisted of elements such as Fe, Cr, and B from the analysis of the X-ray diffraction measurement.
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  • Influence of Processing Temperature on Boriding of SUS304 Stainless Steel by B Added Fused Salt Bath
    Shinji Koyama, Tatsuya Fukuda, Kentaro Kawasumi, Ikuo Shohji
    Article type: Regular Article
    2011 Volume 75 Issue 12 Pages 684-689
    Published: 2011
    Released on J-STAGE: December 01, 2011
    DOIhttps://doi.org/10.2320/jinstmet.75.684
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      The austenitic stainless steel is excellent in corrosion resistance, toughness, and workability. But it is inferior to hardness and wear resistance. However, because it is not possible to stiffen by quenching, the development of the method of improving wear resistance is required. Recently, boriding has attracted extensive attention as surface stiffening processing of plain steel. In this research, the influence of processing temperature on the formation layer of SUS304 steel by B added fused salt bath was examined. Boriding were performed in molten borax which contained 4 mass%B at processing temperatures of 1123~1223 K (processing time of 1800 s). As a result of the examination, the hardness of the boriding layer becomes about 2000 HV when the processing temperature of 1223 K. Also the wear resistance too has improved remarkably. Furthermore, it was understood that the formation layer on the surface was FeB, and, additionally, consisted of compounds such as Fe, Cr, and B from the Vickers hardness and the analysis of the X-ray diffraction measurement.
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  • Supercooling of Homogeneous Liquid Phase of Liquid Metals and Alloys
    —Poor Supercooling around the Eutectic Composition of Liquid Ni-Nb System—
    Toshio Itami, Junpei Okada, Yuki Watanabe, Takehiko Ishikawa, Shinichi ...
    Article type: Regular Article
    2011 Volume 75 Issue 12 Pages 690-696
    Published: 2011
    Released on J-STAGE: December 01, 2011
    DOIhttps://doi.org/10.2320/jinstmet.75.690
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      To study the supercooling of many liquid metals with high melting temperatures, the investigation was performed for the cooling curves of electrostatic levitation (ESL) experiments, which had been originally obtained for the measurements of many physical properties. The largest supercooling over the literature values was found for liquid Ru (428 K), Ta (721 K), W (601 K), and Ir (438 K), where temperatures in the parentheses mean the supercooling of respective liquid metals. This indicates the validity of ESL for the supercooling experiments of liquid metals and alloys because of being rather free from the heterogeneous nucleation. This ESL was applied to the study of supercooling of homogeneous liquid phase in the composition range from 29 at% Nb to 71 at% Nb of eutectic Ni-Nb system, whose eutectic point is present at 40.5 at% Nb and 1448 K. The experimental result shows a poor supercooling tendency of homogeneous liquid phase around the eutectic composition in spite of large supercooling far apart from this eutectic composition. This characteristic feature was discussed based on the classical nucleation theory coupled with the knowledge recently found, the existence of concentration fluctuations in the homogeneous liquid phase near the eutectic point.
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  • Surface Nitriding and Improvement of Wear Resistance of Titanium Using Laser Irradiation
    Tomiko Yamaguchi, Yutaka Yonesho, Kazumasa Nishio
    Article type: Regular Article
    2011 Volume 75 Issue 12 Pages 697-704
    Published: 2011
    Released on J-STAGE: December 01, 2011
    DOIhttps://doi.org/10.2320/jinstmet.75.697
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      Pure titanium is a biocompatible material that is also useful in high-temperature environments, however, wear resistance of the pure titanium is weak. To improve the wear resistance of pure titanium, surface modification is performed using laser beam heating under various laser conditions. The modified surface layer produced by laser melting consists of titanium nitride (TiN), which improves the hardness and the wear resistance. However, the surface of this modified layer is not flat.
      In this study, the laser irradiation was performed in a controlled atmosphere and the effects of the atmosphere on the microstructure, hardness, and wear resistance of the irradiated region were investigated. As the pure titanium surface was heated by laser irradiation, a TiN film was formed on its surface without the introduction of cracks. A lamellar structure was also observed under the TiN film. The maximum TiN thickness obtained without cracking or peeling of the base metal was approximately 13 µm. In comparison with the base metal, the hardness and wear resistance of the TiN film were approximately 8 and 22 times higher, respectively.
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Letters to the Editor
  • Precipitation of Nano-/Micro-Rod Shaped Carbide on Alloy Steel by Plasma Discharge
    Masahiko Kato, Masato Hayashi, Hiroyuki Akebono, Atsushi Sugeta
    Article type: Letters to the Editor
    2011 Volume 75 Issue 12 Pages 705-707
    Published: 2011
    Released on J-STAGE: December 01, 2011
    DOIhttps://doi.org/10.2320/jinstmet.75.705
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      It was newly found that nano-/micro-rod was formed on tool steel substrate by plasma discharging. Solution treated alloy steels were plasma discharged using an RF power source with introducing Ar gas and water into the chamber. Nano-/micro-rods with the length ranging from 1 to 10 µm and width ranging from 0.1 to 3 µm were formed on the surface of the specimen, and the maximum length was obtained for a discharging time of 0.6 ks. From the X-ray diffraction analysis and the electron probe micro analysis, the nano-/micro-rod was identified as chromium carbide.
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