塑性と加工
Online ISSN : 1882-0166
Print ISSN : 0038-1586
ISSN-L : 0038-1586
62 巻, 731 号
選択された号の論文の2件中1~2を表示しています
論文
  • 伊東 篤志, 山戸 正敏, 鳥塚 史郎
    原稿種別: 研究論文
    2021 年 62 巻 731 号 p. 177-182
    発行日: 2021年
    公開日: 2021/12/25
    ジャーナル フリー

    The image analysis tensile test method was applied to obtain true stress-true strain curves at elevated temperature in Ti-6Al-4V alloy. A CCD camera successfully captured the profile change of a specimen during the tensile test. Minimum radius and neck curvature can be calculated from the profile, then used to determine true strain and true stress after necking using Bridgman’s equation. True stress-true strain curves up to a strain of 0.8 were obtained in the high temperature tensile test at 850 ℃. The true stress-true strain curves show work hardening at a strain rate of 0.2 s-1 and dynamic restoration at a strain rate of 0.01 s-1 in the tensile test at 850 ℃. On the other hand, in compression tests, the true stress-true strain curves show steep decrease in true stress after yielding. This might be due to the effect of barreling of the specimen, rather than any metallurgical structural change. The image analysis tensile test method is applicable to obtain accurate high-temperature true stress-true strain curves at elevated temperature up to large strain extent.

  • Masaru UENOHARA, Michihiro SAKO, Masaya ARAI, Yoshiaki NAOI, Yoshiaki ...
    原稿種別: research-article
    2021 年 62 巻 731 号 p. 183-189
    発行日: 2021年
    公開日: 2021/12/25
    ジャーナル フリー

    High-pressure compaction was investigated as a consolidation technique for the fabrication of high-density Zn/samarium-iron-nitrogen (Sm-Fe-N) bulk magnets. To achieve a relative density (dr) above 90.0% in Zn/Sm-Fe-N bulk magnets, we examined the compaction characteristics of Zn/Sm-Fe-N powders within a compaction pressure range of 1.5 to 4.1 GPa, which have not been sufficiently investigated. Furthermore, the effects of compaction pressure and Zn addition on dr were investigated at various concentrations of Zn, and various compaction conditions were evaluated mainly based on the resulting dr. The dr exceeded 90.0% under a pressure of 3.5 GPa in warm compaction at 200 ℃, and significant die breakage was suppressed. The proposed compaction conditions are more suitable for mass production in the vehicle industry than those of conventional techniques. Combining the proposed compaction conditions with 10 wt% Zn, the magnetic properties of the fabricated Zn/Sm-Fe-N bulk magnet show a remanence (Br) of 0.79 T, which represents the residual magnetic flux density, and a coercivity (HcJ) of 1163 kA·m-1, which is an index of the heat resistance of the magnets.

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