Yielding behavior and change in dislocation substructure in an UltraLow carbon martensitic steel

Koichi Nakashima, Yoshitomo Fujimura, Hiroyasu Matsubayashi, Toshihiro Tsuchiyama, Setsuo Takaki

    研究成果: Contribution to journalArticle査読

    58 被引用数 (Scopus)

    抄録

    As-quenched martensitic steels exhibit a unique yielding behavior characterized by very low elastic limit. This phenomenon deeply relates to the behavior of mobile dislocations which have been introduced by martensitic transformation. In order to clarify the effect of mobile dislocations on the yielding behavior of martensitic steels, tensile testing, measurement of dislocation density by X-ray diffractometry and TEM observation were carried out in an ultralow carbon martensite (Fe-18% Ni alloy). And then the effect of dislocation strengthening on the yield stress was also discussed in terms of Bailey-Hirsch relationship. Elastic limit and 0.2% proof stress are very low in the as-quenched martensite, however slight pre-straining to the martensite has caused a marked increase in the both properties despite of a significant decrease in dislocation density. It is also confirmed that slight prc-straining to the martensite causes a clear microstructural change from randomly distributed dislocations to cellar tangled dislocations. These results suggest that mobile dislocations in martensite can easily disappear through the dislocation reaction and remained dislocations form cellar tangled structure in the early stage of tensile deformation. The Bailey-Hirsch plot for 0.2% proof stress indicated that the data of pre-strained martensite are just on the line extended from the data of cold-worked ferritic iron, while that of as-quenched martensite is obviously lower than the value expected from the Bailey-Hirsch relationship. This means that mobile dislocations in martensite do not contribute to dislocation strengthening but only make the yield stress lower through the generation of plastic strain.

    本文言語英語
    ページ(範囲)459-465
    ページ数7
    ジャーナルTetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan
    93
    6
    DOI
    出版ステータス出版済み - 6 1 2007

    All Science Journal Classification (ASJC) codes

    • 凝縮系物理学
    • 物理化学および理論化学
    • 金属および合金
    • 材料化学

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