高Mn鉄合金におけるγ→εマルテンサイト : 変態による軟化と硬化

概要

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The effect of fcc(γ)→hcp(ε)martensitic transformation on the tensile deformation behavior of Fe-Mn-Fe-Mn-Si and Fe-Mn-Co alloys was investigated. The amount of ε martensite formed during deformation was drastically increased by the addition of Si or Co which lowers the Neel temperature. On the otter hand, the Si addition was revealed to suppress the γ→εtransformation by cooling. A positive temperature dependence of 0.2% proof stress resulting form the γ→εtransformation was found above M_s temperature commonly in these three alloy systems. This phenomenon became more pronounced according to an increase in γ strength by Si solid solution and/or dislocation(ausforming)hardening. A pre-existing ε plate was found to be a strong barrier for further plastic flow, so that a high work hardening was produced. Therefore, the tensile property us temperature relation for the alloys examined were well understood by considering the linked influences of softening and hardening due to the deformation inducedγ→ε transformation. Although the shape of the true stress us true strain curve accompanying the γ→ε transformation became unusual one particular to the so-called TRIP(transformation induced plasticity), ductility was not enhanced so much.
社団法人日本材料学会の論文
1991-01-15