Journal of the Japan Society of Powder and Powder Metallurgy
Online ISSN : 1880-9014
Print ISSN : 0532-8799
ISSN-L : 0532-8799
Volume 66 , Issue 7
July
Showing 1-8 articles out of 8 articles from the selected issue
Paper
Memorial Lecture of JSPM Award
  • Naokuni MURAMATSU, Takashi GOTO
    2019 Volume 66 Issue 7 Pages 317-322
    Published: July 15, 2019
    Released: July 15, 2019
    JOURNALS RESTRICTED ACCESS

    High-strength and high-electrical-conductivity hypoeutectic Cu-Zr alloys have been developed. The authors succeeded in balancing characteristics well in a wide range of mechanical strength and electrical conductivity by using dispersion strengthening and fiber reinforcing techniques in nano scale. These have been put to practical use by first processing hypoeutectic Cu-Zr alloy cast-material into ultra-fine wires, and are applied to various cable and wire-electrode applications. In contrast, SPS (Spark Plasma Sintering) material using commercially available powders as a raw material is in practical use as a bulk material. The history of development of hypoeutectic Cu-Zr alloys from their alloy design, their manufacturing process, and the development of eutectic/hypereutectic Cu-Zr alloy SPS material are shown in this paper.

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Paper
  • Yasushi SUGAWARA, Shigeaki SUGIYAMA, Kiyoshi FUDA
    2019 Volume 66 Issue 7 Pages 323-329
    Published: July 15, 2019
    Released: July 15, 2019
    JOURNALS RESTRICTED ACCESS

    Powders of TiO2 mixed with TiB2 of mmol% (m = 0, 1, 2, 3, 4, 5, 10, 12, 20) were prepared, and sintered by using an spark plasma sintering apparatus, the chemical reaction between TiO2 and TiB2 in the sintering process was investigated. In the case of m = 2 to 20, it was found TiO2 was reduced by TiB2, to form and the Magneli phases (TinO2n−1 (n = 3, 4, 5, 6)). The maximum value of the dimensionless figure of merit ZT was 0.18 at 800°C for m = 3, and almost the same value as that of the TiO2-TiN sintered bodies was obtained. The effective carrier concentrations in the TiO2-TiB2 sintered bodies were estimated from Heikes’s formula was about 2.4 times larger than those of the TiO2-TiN, TiO2-TiC, TiO2-VC sintered bodies. The electron mobility μ tends to increase as m increases. The thermal conductivity was dominated by the lattice thermal conductivity at m = 0, while the electronic thermal conductivity was suggested at m = 4 and 5. It was confirmed that the formation of the magneli phase contributes to the improvement of ZT.

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  • Tomoyuki UENO, Keita SHINAJI, Takashi SEKIYA, Yuuki ADACHI, Tetsuya HA ...
    2019 Volume 66 Issue 7 Pages 330-338
    Published: July 15, 2019
    Released: July 15, 2019
    JOURNALS RESTRICTED ACCESS

    In accordance with the principles of the cutting phenomenon, following utilizing computational science, we developed an excellent-machinability additive which dramatically improves the machinability of sintered components. We have demonstrated that the developed excellent-machinability additive can reduce the tool wear in each corresponding tool dramatically to 1/6 to 1/12 in outer periphery machining processes assuming outer diameter processing, undercut grooving and so forth, using a cermet, K grade carbide and CBN tools, which are popularly used in machining of sintered parts. This article reports on the details about the above study.

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  • Ken HIROTA, Masashi YOSHIDA, Xiaoteng GE, Yuta KOSUGA, Masaki KATO, Hi ...
    2019 Volume 66 Issue 7 Pages 339-348
    Published: July 15, 2019
    Released: July 15, 2019
    JOURNALS RESTRICTED ACCESS

    In order to produce ceramic composites having both high Vickers hardness Hv ≥20 GPa and high fracture toughness KIC ≥10 MPa·m1/2, dense TiB2/[ZrO2-Al2O3] composites have been fabricated using pulsed electric-current pressure sintering (PECPS) at 1873 K under 50 MPa for 6.0 × 102 s in Ar. As the former starting materials, two kinds of TiB2 powders were adopted; i) mono-modal particle size (Ps) distribution with an average particle size <Ps> of 3.24 μm and ii) bi-modal Ps distribution with <Ps> of 3.06 μm, composed of the small Ps of 0.58 and the large Ps of 3.27 μm. On the hand, the latter was the mixed powders composed of ZrO2(2.5 mol%Y2O3) solid solution (ss) and α-Al2O3 powders: each primary Ps was 0.1~0.2 μm. Thus fabricated composites consisting of TiB2, tetragonal/monoclinic ZrO2 and α-Al2O3 with relative densities more than 99.0% showed improved mechanical properties, especially bi-modal TiB2/[ZrO2-Al2O3] composites revealed high Hv of 22.3 GPa and KIC of 12.8 MPa·m1/2. These high-mechanical behaviors might be explained in terms of i) better powder particle configuration, ii) high chemical stability of TiB2, iii) the most proper composition, with adoption of iv) bi-modal TiB2 powder and v) the most suitable sintering condition.

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