Plasticity-Induced Martensitic Transformation in Austenitic Stainless Steels SUS 304 and SUS 316 L at Room and Liquid Nitrogen Temperatures (Quantitat

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1 Plasticity-Induced Martensitic Transformation in Austenitic Stainless Steels SUS 304 and SUS 316 L at Room and Liquid Nitrogen Temperatures (Quantitative Measurement using X-ray Diffraction Method) Yoshifumi IWASAKI*5, Yuji NAKASONE, Tetsu SHIMIZU and Noboru KOBAYASHI Department of Mechanical Engineering, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo, Japan The present study investigates plasticity-induced martensitic transformation in two types of austenitic stainless steels SUS 304 and 316 L subjected to uniform tensile stresses at room and liquid nitrogen temperatures. The X-ray diffraction method was used in order to measure volume fractions of transformed martensitic phases and to obtain the dependence of the volume fractions of these phases on the applied strain The difficulty in the measurement of the martensitic phases by the X-ray diffraction method caused by the preferred orientation which had been introduced during the rolling process and during the tensile tests was overcome by the help of Arnell's Method. Two types of target materials, i.e., Cu and Mo for the X-ray source were used to verify the accuracy and reproducibility of the present X-ray diffraction analyses. The results were also compared with those obtained by the saturation magnetization method using VSM, or vibrating-sample magnetometer reported elsewhere. It was revealed transformed in SUS 304 both at 297 and 77 K whereas in SUS 316L only at 77 K. Another type of martensitic phase, was transformed in the both steels only at 77 K. Almost the same values of the volume fractions were obtained by the two types of target materials. volume fraction obtained by the X-ray diffraction methods vs. that by VSM showed a good linear correlation. Key Words : Martensite, Phase Transformation, Stainless Steel, Vibrating Sample Magnetometer, X-ray Diffractometer, Preferred Orientation, Arnell's Method, Material Testing, Plasticity, Tensile Properties rs.kagu.tus.ac.jp

2 Table 1 Chemical compositions of SUS 304 and SUS 316 L stainless steels tested in this study [mass%1 Fig. 1 Specimen geometry (unit : mm)

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