Abstract
Strain-induced martensitic transformation followed by reverse transformation is a possible process to achieve the grain refinement necessary for the superplasticity in austenitic stainless steel SUS304. This process is expected to be applicable also to SUS316L in which working at lower temperature is required for the strain-induced transformation. In this study, the transformation behavior of SUS316L during sub-zero working and annealing was investigated. The grain size of about 1 μm was obtained by the process of 90% sub-zero rolling at liquid nitrogen temperature followed by annealing at 973K for 3600 s. Furthermore, this process condition provided the total elongation of more than 300% and the strain-rate sensitivity index (m value) of 0.3 in the strain rate range from 1.8 to 3.2×10-4/s.
