Journal of the Japan Society of Powder and Powder Metallurgy
Online ISSN : 1880-9014
Print ISSN : 0532-8799
ISSN-L : 0532-8799
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Volume 58, Issue 4
April
Displaying 1-11 of 11 articles from this issue
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Paper
Paper
  • Compacts of Ultra Fine WC Powder by High-Speed Centrifugal Compaction Process and Sintering of them (1st report) -Development of Non-Aqueous Slip of WC-
    Hiroyuki Y. Suzuki, Yuichi Kadono, Hidenori Kuroki
    2011 Volume 58 Issue 4 Pages 201-206
    Published: 2011
    Released on J-STAGE: June 29, 2011
    DOIhttps://doi.org/10.2497/jjspm.58.201
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    A non-aqueous slip system for ultra fine WC powder (100 nm) is developed. Addition of non-ionic surfactant makes possible to disperse WC powders in alkane liquid (heptane), although the suspension is meta-stable, namely, the WC particles sediment gradually with time, because the density of WC is much higher than that of the medium. In such meta-stable slip systems, a lower ultimate sediment height in gravitational sedimentation corresponds to good dispersing state. A slip prepared by planetary ball milling and compacted by High-speed Centrifugal Compaction Process achieved packing density of 55 %.
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  • Process of Molybdenum Powder Elution in Water
    Masahiro Katoh, Kenji Hayashi, Toshiharu Araki, Masayoshi Yoshida, Mas ...
    2011 Volume 58 Issue 4 Pages 207-213
    Published: 2011
    Released on J-STAGE: June 29, 2011
    DOIhttps://doi.org/10.2497/jjspm.58.207
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    As the starting material of molybdenum manufactured by powder metallurgy, molybdenum powder is used. To investigate the elution in water of the molybdenum powder used as a raw material, the molybdenum elution was analyzed by ion chromatography and X-ray photoelectron spectroscopy (XPS). It was clarified that the elution based on MoO42- takes place as determined by ion chromatography. Results of the surface measurement by XPS revealed that, the molybdenum oxidized in air on the surface exists mainly as molybdenum (VI) oxide (MoO3), which is the most stable oxide. The molybdenum (VI) oxide elutes promptly in water compared with the metal powder. The oxide on the molybdenum metal surface, which was assumed to be eluted promptly, became thin, and the elution was repeated again by oxidation in water through molybdenum (IV) (MoO2), (V) (Mo2O5) and (VI) oxides, and the solution was clarified to elute through molybdenum (VI) oxide.
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  • Simultaneous Synthesis and Sintering of Al2O3/TiN Composites using Capsule-free N2-HIPing from Al2O3 and Fine Ti mixed Powder Compacts
    Hajime Yagura, Katsuya Takaoka, Masaki Kato, Ken Hirota, Toshinori Fuj ...
    2011 Volume 58 Issue 4 Pages 214-219
    Published: 2011
    Released on J-STAGE: June 29, 2011
    DOIhttps://doi.org/10.2497/jjspm.58.214
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    Synthesis of dense composite materials with the compositions of Al2O3/TiN=100/0∼90/10 vol% has been attempted directly from Al2O3/Ti mixed raw powder compacts using capsule-free N2 hot isostatic pressing (HIP). Fine Ti powders (0.3 μm in diameter) with a small amount of TiN0.3 phase were prepared by thermal decomposition of fine TiH2 powders at 400°C for 3.6×103 s in a vacuum, followed by thermal treatment in N2. Then, Al2O3/Ti mixed powder compacts with homogeneously dispersed Ti particles were fabricated and then HIP-sintered. During the first stage of HIPing [1350°C/6 MPa/3.6×103 s], solid/gas reaction between Ti and N2, in which both were contained in the powder compacts, was introduced to form TiN. Then, after the successive second stage of HIPing [1350°C/196 MPa/7.2×103 s], the most of sintered composites consisting of Al2O3 and TiN phases reached to a higher relative density than 98.5 % with closed pores, nevertheless a capsule-free HIPing. Dispersion of TiN particles (0.30∼0.35 μm) just formed suppressed the grain growth of Al2O3 during sintering. Mechanical properties, such as bending strength (σb), Vickers hardness (HV), and fracture toughness (KIC) have been evaluated as a function of TiN content.
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Memorial Lecture of JSPM Award
  • Development of Atmosphere-Control HIP Processes and Equipment
    Takao Fujikawa, Yasuo Manabe
    2011 Volume 58 Issue 4 Pages 220-224
    Published: 2011
    Released on J-STAGE: June 29, 2011
    DOIhttps://doi.org/10.2497/jjspm.58.220
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    Hot Isostatic Pressing (HIP) of ceramics has been recognized as an ideal process to produce fully dense and highly reliable parts in the course of the application to ferrite magnetic recording heads, alumina cutting tool inserts, and automobile engine parts made of silicon nitride. Usually, these parts are processed by the so-called capsule-free method in which the processed parts are directly exposed to the pressure medium gas. In this case, some interactions between the processed material and the gas may occur and this phenomenon has to be carefully considered for some nitrides and oxides. Therefore, the influence of the surrounding gas as an atmosphere is discussed from the viewpoint of thermo-dynamics. Three practical methods to create the desired atmosphere are described and some examples in the application are given for silicon nitride, superconductive ceramics and calcium carbonates. In addition the development of the HIP equipment which can create desired atmosphere will be briefly reviewed.
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Special Issue:Development of Innovative Materials by Mechanical Alloing
Summarization
Paper
  • Effect of Mechanical Alloying Conditions on Mechanical Properties of Ti-HAp Composite Materials
    Takuya Ohno, Masahiro Kubota
    2011 Volume 58 Issue 4 Pages 227-232
    Published: 2011
    Released on J-STAGE: June 29, 2011
    DOIhttps://doi.org/10.2497/jjspm.58.227
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    Ti-x HAp (x=10, 20 and 30 mass%) composite powders were synthesised by mechanical alloying (MA) using a vibrational ball mill, and MAed composite powders were consolidated into bulk composite materials by spark plasma sintering (SPS). Effects of MA conditions on the hardness and constituent phase of the MAed powder and SPS materials were investigated by hardness measurements and X-ray diffraction (XRD), respectively. No decomposition of HAp in the Ti-HAp composite powders was observed, whereas formation of CaO was observed in all the SPSed materials. In addition, formation of TiC occurred in the Ti-10 and 20 HAp SPSed materials. On the other hand, both CaTiO3 and TiN was formed in the Ti-30 HAp SPSed materials. The hardness of the Ti-HAp SPSed materials fabricated from the 0.5, 1 and 2 h MAed powders were higher than that of the pure Ti SPSed materials fabricated from the none MAed powder. A maximum value of Vickers hardness was 1101 HV when the Ti-20 HAp SPSed material was fabricated from 1 h MAed powder.
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  • Synthesis of Fe-48at%Cr Alloy by a Short-time Process using Fast-rotating Planetary Ball Milling
    Haruka Morishita, Hiroyuki Nakayama, Kimihiro Ozaki, Keizo Kobayashi
    2011 Volume 58 Issue 4 Pages 233-236
    Published: 2011
    Released on J-STAGE: June 29, 2011
    DOIhttps://doi.org/10.2497/jjspm.58.233
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    Fe-48at%Cr powder was synthesized by mechanical alloying (MA) of Fe powder and Cr powder using rapid-rotation type planetary ball mill. Homogeneous MA powder was obtained for only 600 s milling at 900 rpm of orbital speed while it had taken for over 360 ks to homogenize them at 200 rpm. The obtained powder had a crystal structure of bcc lattice and contained no brittle phase such as σ phase. The MA powder was sintered by a pulsed current sintering and completely condensed above 1000 K. The sintered Fe-48at%Cr alloy also has no σ phase. Hardness of the sintered body is Hv 380 and there was no crack around the indentation for Vickers hardness.
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  • Fabrication of Magnesium Based Composite Powders with High Hardness and Hard Magnetic Properties by Mechanical Alloying
    Sho Aoki, Masahiro Kubota
    2011 Volume 58 Issue 4 Pages 237-242
    Published: 2011
    Released on J-STAGE: June 29, 2011
    DOIhttps://doi.org/10.2497/jjspm.58.237
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    In order to fabricate Mg-based composite powders with high hardness and hard magnetic properties, pure magnesium and barium ferrite powders were mechanically alloyed (MAed) using a vibrational ball mill.
    Change in Vickers micro-hardness of the pure magnesium powders as a function of the mechanical milling (MM) times obeyed the crystallite size. Change in Vickers micro-hardness of the composite powders as a function of the amount of barium ferrite obeyed the rule of mixture when the MA time was 120 and 240 min.. On the other hands, change in Vickers micro-hardness of the composite powders as a function of the amount of barium ferrite wasn't obeyed the rule of mixture when the MA time was 20 and 60 min.. Magnetization of the composite powders obeyed the amount of the barium ferrite powder, whereas coercive force of the MAed powders decreased due to the refinement of the barium ferrite powder.
    Mg-based composite powders with high hardness and hard magnetic properties were successfully produced by mechanical alloying.
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