著者

村田 純教 Murata Yoshinori

巻号頁・発行日

1982-03-25 (Released:2006-06-15)

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名古屋大学博士学位論文 学位の種類:工学博士 (課程) 学位授与年月日:昭和57年3月25日

著者

村田 純教

出版者

公益社団法人 日本金属学会

雑誌

日本金属学会誌 (ISSN:00214876)

巻号頁・発行日

vol.80, no.11, pp.669-683, 2016 (Released:2016-10-25)

参考文献数

57

被引用文献数

3

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Lath Martensite is formed in low carbon steels and plays an important role in the mechanical properties of heat resistant steels containing about 0.1 mass%C. The lath martensite shows the hierarchic microstructure being composed of packet, block and lath. Martensitic transformation is the phase transformation accompanying orderly shear deformation without atomic diffusion. Relaxation of the strain energy caused by the deformation is the origin of the hierarchic microstructure but the formation mechanism of this microstructure has heretofore not been understood. In this paper, we survey first both the experimental results and phenomenological formation mechanism of the lath martensite reported so far and introduce a new mechanism (Two Types of Slip Deformation model: TTSD model), which is constructed by considering, independently, two kinds of slip deformations using the slip deformation model proposed by Khachaturyan. It is also introduced that TTSD model enables us to simulate the martensite phase formation by the phase-field method. Furthermore, it is found that TTSD model allow us to predict the features of lath martensite, such as the existence of sub-blocks and high dislocation density in lath. In particular, for the first time, the reason why laths in a block structure exist, can be clearly explained by TTSD model.

著者

村田 純教 鷹見 恭平 神谷 美紗紀 森永 正彦 橋詰 良吉 三木 一宏 東 司 石黒 徹

出版者

社団法人日本鉄鋼協会

雑誌

鐵と鋼 : 日本鐡鋼協會々誌 (ISSN:00211575)

巻号頁・発行日

vol.88, no.4, pp.214-221, 2002-04

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In recent advanced high Cr ferritic steels, it is known that the Laves phase precipitates during creep test when the steels contain a relatively high level of Mo+W content. The Laves phase is believed to be granular in shape and to exist in the boundaries of lath, block, packet and prior austenite grains, but a number of fine Laves-phase precipitates are found to exist even inside the martensite lath in the tempered steels containing 10 mass% Cr and 4.6 mass% W. The shape of this Laves phase is plate-like, and the size is below 300 nm. The crystallographic relationship between the fine Laves phase and the matrix phase is as follows; (111)_<ferrite>//(001)_<Laves> and [01^^-1]_<ferrite>//[110]_<Laves>. In the microstruc ture aged at 923 K for 7〜14 Ms, the fine precipitates of the Laves phase disappear inside the martensite lath, and coagulated Laves phase is observed at the lath-, block-, or packet- boundaries. Only the low C steel containing 0.08% C and 3% W shows a few amounts of the fine precipitates of the Laves phase after aging at 923 K for 7.268 Ms. This compositional dependence of the precipitation behaviour can be understood qualitatively with the aid ofthe System-Free-Energy Concept.