Discontinuous Yielding of Metastable Austenitic Stainless Steel

摘要

Constant straining rate and constant loading rate tensile tests were performed on stable and unstable austenitic stainless steels. The results shown that under certain conditions of temperature, testing speed and environment, the stress strain curves of the unstable alloy, Type 301 stainless steel, are stepped or serrated depending upon whether the test was performed under constant rate of loading or constant rate of straining. Discontinuous yielding occurred almost exclusively in the range where the flow stress is a decreasing function of strain rate. The decrease of flow stress with increasing strain rate is a result of a time-temperature dependent martensitic transformation of the metastable austenite. For the stable alloy, Type 316 stainless steel, the flow stress always increased with strain rate and the corresponding stress strain curves were smooth. (Author)