Influence of the martensitic transformation on the deformation behaviour of an AISI 316 stainless steel at low temperatures

Abstract

The deformation behaviour of an AISI 316 stainless steel under uniaxial tension was examined at 25, − 70 and − 196° C. The flow curves exhibited peculiar shapes and the work hardening rates were found to increase with strain beyond certain values of plastic strain. X-ray diffraction analyses showed that the transformation toα-martensite commenced at these values of plastic strain and thereafter the volume fraction ofα increased steadily with strain. On the other hand, the amount of the∈-martensite was found to increase with plastic strain initially, reach a maximum and then decrease gradually. The contribution of theα-phase to the flow stress of the alloy was found to be directly proportional to the volume fraction ofα. It is shown that the analysis of the flow curves provides a simple method of detecting the onset of the strain-induced martensitic transformation as well as estimating the amount of this martensite during further deformation.