| Summary: | 碩士 === 國立中山大學 === 材料與光電科學學系研究所 === 107 === This thesis studies the effect of deformation temperature and plastic strain on the tensile properties and microstructure of a medium manganese steel. The strain rate used was 10-2/s, and the testing temperatures were between room temperature and 275 oC. It was found that highest tensile strength, 0.2% yield strength and elongation were obtained at 25 oC, and a largest amount of strain induced martensite was found at room temperature. At 175 and 275 oC, lowest elongation was obtained, which is due to the lack of strain-induced phase transformation. From SEM microstructural observation, it was found that, between 25oC to 100oC, strain-induced martensite occurred, and the higher the testing temperature, the less amount of strain-induced martensite formed. At 125°C, only a small number of strain-induced martensite was found at regions having area reduction up to 60%, and strain-induced bainite began to be formed. At testing temperatures between 150°C and 275°C, only strain-induced bainite was found. The strength and tensile elongation were found depended on the degree of strain-induced phase transformation.
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