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 78, Issue 10
Displaying 1-5 of 5 articles from this issue
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Regular Article
  • Infiltration of Magnesium-Zinc and Magnesium-Aluminum Alloys into Titanium Powder Preforms Using Indirect Selective Laser Sintering
    Atsushi Yamaguchi, Tomoki Tomita, Shinji Fukumoto
    2014 Volume 78 Issue 10 Pages 369-374
    Published: 2014
    Released on J-STAGE: October 01, 2014
    DOIhttps://doi.org/10.2320/jinstmet.J2014006
    JOURNAL FREE ACCESS
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      In this study, we attempted to infiltrate molten magnesium-zinc (Mg-6.2 mass%Zn) alloy and magnesium-aluminum (Mg-8.3 mass%Al) alloy into titanium powder preforms using indirect selective laser sintering (SLS). It was observed that molten Mg-Zn and Mg-Al alloys could easily infiltrate the Ti powder preforms during self-activation at 973 K under argon atmosphere. In addition, all of the infiltrated sections of the preforms were found to exhibit excellent dimensional accuracy.
      The hardness and tensile strength of the infiltrated portions of Mg-Zn were found to be 71 HRB and 333 MPa, respectively, and the corresponding values for Mg-Al alloy were 71 HRB and 343 MPa, respectively. The tensile strengths of the parts of the preform infiltrated with an alloy were significantly higher than those of the parts infiltrated with just Mg (241 MPa). We believe that the large increase in tensile strength after Mg-Zn and Mg-Al infiltration is due to the interfacial reinforcement of the matrix and the generation of Ti-based intermetallic phases, such as TiZn3, TiAl, and Ti3Al, on the surface of Ti particles as a result of their reaction with molten alloys. As a consequence of the reaction with molten alloys, the Zn or Al concentration in the infiltrated parts of the matrix was found to be lower than before infiltration. Thus, the infiltration of the Mg-Zn and Mg-Al alloys into Ti powder preforms can be considered an effective indirect SLS technique for producing lightweight infiltrated metal alloy parts.
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  • Relationship between Morphology of Strain-Induced Martensite Phase and Magnetic Properties in Austenitic Stainless Steels
    Kodai Miura, Satoru Kobayashi, Yasuhiro Kamada, Yusuke Onuki, Jerzy A. ...
    2014 Volume 78 Issue 10 Pages 375-380
    Published: 2014
    Released on J-STAGE: October 01, 2014
    DOIhttps://doi.org/10.2320/jinstmet.JAW201405
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      We have performed high-sensitivity magnetic measurements for tensile-deformed SUS304-type austenitic stainless steel to elucidate a relationship between morphology of martensite particles and structure-sensitive magnetic hysteresis properties. A monotonic increase of the volume fraction of martensite phase up to 14.3% through strain-induced martensitic transformation was observed, while coercivity exhibits a maximum at around 4.3% fraction. Measurements of coercivity varying the magnetic-field direction against tensile direction revealed anisotropy in angular dependence of coercivity that becomes weaker with the progress of plastic deformation. These observations were explained as due to a change of the size and anisotropy in shape of martensite phase with deformation.
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  • Detection of Crack Propagation by AE and Evaluation of Fracture Toughness in Various Mg Alloys
    Yuki Muto, Kousuke Matsumoto, Takayuki Shiraiwa, Manabu Enoki
    2014 Volume 78 Issue 10 Pages 381-387
    Published: 2014
    Released on J-STAGE: October 01, 2014
    DOIhttps://doi.org/10.2320/jinstmet.JAW201401
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      The simple method for evaluation of fracture toughness in Mg alloys was examined by AE. In this study, fracture toughness (KIAE) in AZ31 (Mg-9Al-1Zn), AZ91 (Mg-9Al-1Zn), and LA141 (Mg-14Li-1Al) was investigated. Specimens (L-S, T-S) were machined from as-rolled AZ31, LA141, and as-cast AZ91. Four-point-bending tests were conducted according to ASTM E-399 with AE measurement, and the crack pass was observed by microscope during the testing. KIC was supposed to be the value of KI when the crack initiates from the tip of the pre-crack. KIAE was defined as the value of KI when the RMS voltage of AE indicated the maximum value before ultimate load. The crack propagation was observed by microscope at the time of RMS peak. The values of KIAE were 12.4-15.0 (AZ31), 11.5-11.7 (AZ91), and 24.7-28.0 (LA141) [MPa m1/2]. Compared with reference data, the fracture toughness in Mg alloys estimated by KIAE was adequate. The possibility of the simple method for evaluation of fracture toughness in Mg alloys by AE was demonstrated.
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  • Effects of Hardness of Shot Peening Media on Surface Modification Behavior of Gas Carburized Steel by Micro Shot Peening
    Toshiyuki Sawada
    2014 Volume 78 Issue 10 Pages 388-394
    Published: 2014
    Released on J-STAGE: October 01, 2014
    DOIhttps://doi.org/10.2320/jinstmet.J2014004
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      Effects of the hardness of fine media used in shot peening on the surface modification behavior of workpiece with high hardness were investigated. Gas carburized JIS-SCM822 steels with the surface of 720 HV in Vickers hardness were shot peened by fine media with the range from 390 to 1550 HV in Vickers hardness, followed by the examination of their surface modification behavior.
       Shot peening was carried out by using suction-type air peening machine with 0.6 MPa in air pressure, 10 s in peening time and 50 mm in peening distance. Various gas atomized powders sieved from 45 to 125 μm in particle diameter were used as fine peening media.
       On the peened surface by the fine media with remarkably higher hardness than that of workpiece, deep nanocrystalline layer with around 1 μm in depth and less than 15 nm in grain size was generated. In these nanocrystalline layers, the thickness increased and grain size decreased with increasing Vickers hardness of used peening media. In addition, Vickers hardness on peened surface also increased with increasing Vickers hardness of used peening media. Especially, the hardening effect on peened surface was outstanding, in the case of using fine peening media with more than 1020 HV in Vickers hardness. It seemed that this hardening effect was caused by grain refinement strengthening in nanocrystalline layer.
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  • Measurements of the Solubility of Fe2O3 and Cr2O3 in Fused Na2O-B2O3 Salts at 1173 K
    Ryutaro Toki, Takashi Doi, Nobuo Otsuka
    2014 Volume 78 Issue 10 Pages 395-399
    Published: 2014
    Released on J-STAGE: October 01, 2014
    DOIhttps://doi.org/10.2320/jinstmet.JAW201402
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      Solubility of Fe2O3 and Cr2O3 powder to binary fused Na2O-B2O3 salt system was measured at 1173 K in air. Basicity of the melt was continuously monitored by the basicity sensor with an oxide ion probe and zirconia oxygen probe. Basicity of the fused salt was varied from 10.3 to 14.5 by adding B2O3 powder. For the entire range of the tested basicity, solubility of Fe2O3 was one order of magnitude higher than that of Cr2O3. Solubility of both Fe2O3 and Cr2O3 decreased with increasing the basicity of the melt. From the solubility dependence on the melt basicity, both Fe2O3 and Cr2O3 are suggested to dissolve by the basic dissolution reaction.
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