著者

郭 光植 山室 賢輝 峯 洋二 森戸 茂一 高島 和希

出版者

一般社団法人 日本鉄鋼協会

雑誌

鉄と鋼 (ISSN:00211575)

巻号頁・発行日

pp.TETSU-2023-076, (Released:2023-11-25)

参考文献数

24

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Microtensile and microfracture tests were performed on the sharp-edge regions of Japanese swords fabricated in the Muromachi and Showa periods, which are called old sword (OS) and modern sword (MS), respectively, to correlate the mechanical properties with the inhomogeneous microstructures. The hardness of the sharp-edge regions was characterised by the distribution of fine pearlite mixed in martensite microstructures. The OS containing a large fraction of fine pearlite exhibited a low hardness compared to the MS. Microtensile tests using sharp-edge specimens revealed a positive correlation between their tensile strength and strain-to-failure, as opposed to the common tendency in conventional carbon steels made by modern iron-making technology. The fracture surfaces of the sharp-edge specimens were composed of intergranular and dimple fracture features. The tensile strength and dimple fracture area fraction were higher in the OS than in the MS. These findings suggest that the fine pearlite microstructure contributes to increased strength in the sharp-edge region through inhibiting the linkage of intergranular cracking owing to local plastic deformation. Microfracture tests using the sharp-edge specimens revealed that the intrinsic fracture resistance of both OS and MS was determined by the intergranular fracture, whereas the fine pearlite microstructure increased the resistance to crack propagation. The micromechanical testing study indicates that in the sharp-edge regions, their strength and fracture toughness are simultaneously enhanced by the presence of fine pearlite although depending on its distribution.

著者

牧 正志 古原 忠 辻 伸泰 森戸 茂一 宮本 吾郎 柴田 曉伸

出版者

一般社団法人 日本鉄鋼協会

雑誌

鉄と鋼 (ISSN:00211575)

巻号頁・発行日

vol.100, no.9, pp.1062-1075, 2014 (Released:2014-08-31)

参考文献数

72

被引用文献数

24 30

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After ausforming appeared as the first thermomechanical processing of steels in the first half of the 1960 s, various thermomechanical processings have been developed for the improvement of mechanical properties over the last fifty years. Their application was mainly to martensitic steels in the 1960 s such as ausforming and TRIP, and moved to ferrite (+ pearlite) structures by the development of controlled rolling and accelerated cooling of HSLA steels in the 1970~1980 s. However, recently, interest has returned to martensite (and also bainite) because of the demand for higher strength, and the ausforming and TRIP have been revived and successfully applied to commercial practice. Very recently, severe plastic deformation (SPD) is the focus of attention as a new method of producing a very fine-grained structure with grain size of less than 1 μm. By the application of SPD, dynamic phenomena such as dynamic recrystallization and dynamic ferrite transformation occur in the process. We need more systematic studies on such phenomena for the development of new type of thermomechanical processing in steels.

著者

足立 吉隆 森戸 茂一 佐藤 尚

出版者

独立行政法人物質・材料研究機構

雑誌

基盤研究(C)

巻号頁・発行日

2008

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マルテンサイトパケットは互いに複雑に入り組んでいること、その界面は特定の晶癖面を持っていること、またブロックも入り組んだ構造を持っていることが明らかとなった。すべてのブロックは旧オーステナイト粒界に接していた。さらに、三次元像の定量化を位相幾何学および微分幾何学の観点から行うに当たって、種数、オイラー評数、ガウス曲率、平均曲率といったパラメータを導入して、形態の定量化への可能性を検証した。その結果、これらのパラメータを使うことによって、複雑な実際の金属組織形態の定量化が可能であることを示し、今後の新しい3D定量材料組織学構築への布石となるものと期待される。