引張り変形中にオーステナイトステンレス鋼に誘起されるマルテンサイトの体積分率の電気抵抗法による評価と試験片形状依存性

概要

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To estimate the volume fraction of martensite induced in austenitic stainless steel during tensile deformation, the resistivity of a specimen was measured at a temperature of 77, 187 or 293K. Since the distribution of the martensite in the specimen was observed in the specimen having the small slenderness ratio. Accordingly, the specimen having the large slenderness ratio was used to estimate the martensite volume by the resistivity. The negative resistivity region was observed on the resistivity- plastic strain curve regardless of the specimen temperature. It was suggested that the negative resistivity was caused by the formation of ε martensite that is a precursor of the martensite and the process of the resistivity was controlled by the formations of the ε martensite and the microscopic plastic deformation induced by the martensite. The linear relation between the resistivity and the volume fraction of the martensite was confirmed by the experiment and a simple model. It was clarified that the resistivity could be used as an index of estimating the deformation-induced martensite in austenitic stainless steel.