日本金属学会誌
Online ISSN : 1880-6880
Print ISSN : 0021-4876
ISSN-L : 0021-4876
最新号
選択された号の論文の4件中1~4を表示しています
オーバービュー
  • 大村 孝仁, 譯田 真人
    原稿種別: オーバービュー
    2023 年 87 巻 2 号 p. 31-44
    発行日: 2023/02/01
    公開日: 2023/01/25
    [早期公開] 公開日: 2022/12/09
    ジャーナル フリー HTML

    Mechanical behaviors of metallic materials in a small scale are characterized and physically modeled based on experimental measurements and computational simulation. Local plasticity in the vicinity of a grain boundary is considered in terms of an interaction between dislocation and grain boundary. It is shown experimentally that nanoindentation technique can detect a resistance to dislocation slip transfer by a grain boundary with a geometrical or a chemical factor. Molecular dynamic simulation revealed that the geometrical effect depends on not only a misorientation but also a combination with a dislocation character. TEM in-situ straining has a great potential to measure directly a critical stress upon slip transfer as well as a dislocation reaction at a grain boundary. Another potential reaction of a dislocation absorption at a grain boundary was discussed based on both the experimental results by TEM in-situ observation and the atomistic simulation in bcc metals.

    Fig. 1 SPM images of the sample surface including the GB and the indent mark. (a), (b) Gradient images of the sample surface for Σ9{221} and Σ9{114}, respectively. (c), (d) Cross-sectional profiles along the yellow line on the SPM image. The distance d between the triangle center and the GB can be measured as approximately 1 µm on (a) and (b). The length l of the side of the triangle can be measured as shown in (a). A characteristic difference in the shape of the piling up around the indent mark in (c) Σ9{221} and (d) Σ9{114} is shown by orange arrows13). Fullsize Image
     
  • 大村 孝仁, 譯田 真人
    原稿種別: オーバービュー
    2023 年 87 巻 2 号 p. 45-55
    発行日: 2023/02/01
    公開日: 2023/01/25
    [早期公開] 公開日: 2022/12/09
    ジャーナル フリー HTML

    Mechanical behaviors of metallic materials in a small scale are characterized and physically modeled based on experimental measurements and computational simulation. An effect of in-solution carbon or silicon in Fe on a plasticity initiation was characterizes by nanoindentation pop-in phenomenon. A coherency at a ferrite-cementite interface significantly affects to a plasticity initiation leading to a different macroscopic yielding behavior. A stability of an austenite phase in TRIP steel was evaluated though the analysis of indentation-induced deformation behavior, demonstrating a significant constraint effect on stabilization by an adjacent harder phase. Heterogeneous microstructures with a bimodal grain size in fcc metals show an inhomogeneous mechanical behavior depending on a location of the fine microstructure. An intermittent plasticity in pure iron was analyzed through a statistical model showing a Gaussian function by thermally activated process in the early stage and a power-law one by an avalanche type phenomenon in the subsequent stage. An elementally step in a plastic deformation in a metallic glass was characterized through Molecular Dynamics simulation indicating that the plasticity inhomogeneity depends remarkably on the initially inhomogeneous atomistic structure.

    Fig. 1 Examples of the load-displacement curves for Fe-C binary alloys with various carbon contents14). Fullsize Image
     
論文
  • 堀田 善治, 丸野 大輔, 池田 幸将, 増田 高大, 唐 永鵬, 有田 誠, 肥後 祐司, 丹下 慶範, 大石 泰生
    原稿種別: 論文
    2023 年 87 巻 2 号 p. 56-65
    発行日: 2023/02/01
    公開日: 2023/01/25
    [早期公開] 公開日: 2023/01/13
    ジャーナル フリー HTML

    In this study, severe plastic deformation through high-pressure sliding (HPS) was applied for in situ high-energy X-ray diffraction analysis at SPring-8 in JASRI (Japan Synchrotron Radiation Research Institute). Allotropic transformation of pure Ti was examined in terms of temperatures, pressures and imposed strain using a miniaturized HPS facility. The true pressure applied on the sample was estimated from the peak shift. Peak broadening due to local variation of pressure was reduced using white X-ray. The phase transformation from α phase to ω phase occurred at a pressure of ∼4.5 GPa. Straining by the HPS processing was effective to promote the transformation to the ω phase and to maintain the ω phase even at ambient pressure. The reverse transformation from ω phase to α phase occurred at a temperature of ∼110℃ under ambient pressure, while under higher pressure as ∼4 GPa, the ω phase remained stable even at ∼170℃ covered in this study. It was suggested that the reverse transformation from the ω phase to the α phase is controlled by thermal energy.

     

    Mater. Trans. 62 (2021) 167-176に掲載

    In situ synchrotron X-ray diffraction analysis using high-pressure sliding process and application to pure Ti with ω phase formation. Fullsize Image
     
feedback
Top