Journal of the Japan Institute of Metals and Materials
Online ISSN : 1880-6880
Print ISSN : 0021-4876
ISSN-L : 0021-4876
Volume 84, Issue 8
Displaying 1-4 of 4 articles from this issue
Regular Article
  • Keisuke Yamagishi, Daisuke Ando, Yuji Sutou, Yukiko Ogawa
    Article type: Regular Article
    2020 Volume 84 Issue 8 Pages 253-259
    Published: August 01, 2020
    Released on J-STAGE: July 25, 2020
    Advance online publication: May 22, 2020
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    The formation of texture through thermomechanical treatment was investigated in Mg-18.8 at% Sc shape memory alloy to enhance its superelasticity at room temperature. The samples were cold rolled in an α phase or in a β phase and then finally heat treated at 690℃ followed by water quenching to obtain a β phase. In the case of cold rolling in the α phase, a basal-plane texture was formed, while no preferential texture was observed along in-plane direction. After the final heat treatment, {011}<uvw>β transformation texture was obtained, according to Burgers relationship, indicating no improvement of the superelasticity along in-plane direction. In the case of the cold rolling in the β phase, a weak {111}<011>β recrystallization texture was obtained. The sample showed about 0.65% superelastic tensile strain along rolling direction, while that along transverse direction (//~<113>β) showed only about 0.43%. This trend is in good agreement with the orientation dependence on the transformation strain, but, the obtained superelastic strain was much lower than the expected value, which is due to the weak texture and suggests the existence of a strong grain constraint in the Mg-Sc shape memory alloy.

    Graphical Abstract Fullsize Image
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    Young Author Best Paper Award 2021

  • Kouichi Niinobe, Daichi Takeda
    Article type: Regular Article
    2020 Volume 84 Issue 8 Pages 260-269
    Published: August 01, 2020
    Released on J-STAGE: July 25, 2020
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    The lamination cladding of Nb and Al plates with an inserted Ti foil and heat treatment at 973 K, which was higher than the Al melting point, was applied to the development of Nb-Al intermetallic compounds. It was revealed that the uniform region consisting of fine particles with a grain size of below 1 µm and Al was formed in the vicinity of the Nb substrate and gradually grew toward the interior of molten Al, in which TiAl3 particles distributed. EDX analysis and X-ray diffraction examination revealed that the constituent phase of the fine particles is a ternary (Ti,Nb)Al3 of the D022 crystal structure. The molten Al containing Ti may contribute to the formation of the fine particle regions in contact with the Nb substrate. By heating at 973 K, the front of the fine particle regions proceed toward the molten Al, accompanied by the decomposition of the TiAl3 particles distributed in the molten Al, resulting in the uniform growth of the fine particle regions without the TiAl3 particles.

    Fig. (a) An optical image of the ternary Nb-Ti-Al specimen heated at 973 K for 10.8 ks and (b) A SEM image showing the region B in Fig. (a). Fullsize Image
  • Kazuyuki Shimizu, Hiroyuki Toda, Kyosuke Hirayama, Hiro Fujihara, Yosh ...
    Article type: Regular Article
    2020 Volume 84 Issue 8 Pages 270-275
    Published: August 01, 2020
    Released on J-STAGE: July 25, 2020
    Advance online publication: July 03, 2020
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    Hydrogen in materials degrades mechanical properties, which is widely recognized as hydrogen embrittlement. To understand hydrogen embrittlement, it is necessary to clarify the accumulation behavior of hydrogen under stress. The neutron radiography and neutron tomography techniques are applied to examine whether hydrogen accumulation behavior can be visualized directly. Palladium specimens with and without hydrogen were prepared for the neutron imaging experiment under stress. Solute hydrogen has caused distinct contrast change in both the neutron radiography and neutron tomography. Hydrogen distribution at a notch-tip in a loaded specimen has not been visualized in the tomographic cross-sectional images. It can be inferred that this is fundamentally attributable to low spatial resolution of the present imaging set-up, and possibility to visualize hydrogen distribution due to loading is discussed.

    Fig. 7 Virtual cross-sections of the 3D neutron tomographic images; (a) palladium without hydrogen, (b) that with 10% hydrogen, and (c) that with 10% hydrogen after loading. (a) and (b) were observed without loading. (d) Line profiles were obtained from the white solid lines in (a)-(c). Fullsize Image
Technical Article
  • Tomoki Saka
    Article type: Technical Article
    2020 Volume 84 Issue 8 Pages 276-283
    Published: August 01, 2020
    Released on J-STAGE: July 25, 2020
    Advance online publication: June 26, 2020
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    Industrial properties of aluminum alloys are usually increased by having additives in a liquid state which leads to crystal grain refinement. Conventional methods to confirm the effect of the miniaturization are binarization of electron microscope images and electron probe micro analyzer (EPMA) which require enormous man-hours. The purpose of this research is to establish a method for classifying crystals in significantly shorter period. The proposed method is crystal classification per pixel on microscopic images by applying deep learning. In the experiment, the proposed method was performed on Al-Si-Mg alloys with an abundance ratio of 88:11:1, and the results were compared with the correct values created by the conventional EPMA and manual methods. The percentage of accuracy (the intersection over union (IoU)) came out lower than 30% in Mg, but approximately 90% in Si. Therefore, the study shows that this method can be applied with high accuracy if the element is presented in about 10% of the image.

    Electron microscope image and crystal classification of Al-Si-Mg alloy. Fullsize Image
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