Role of Stress-Induced Martensitic Transformation in TRIP Effect of Metastable Austenitic Stainless Steels

Abstract

To investigate the role of stress-induced martensitic transformations in the TRIP effect, stress-strain curves and TRIP effects in two types of metastable austenite steel (JIS-SUS304 and JIS-SUS301L) were compared. In static tensile tests, the tensile strength (TS) of SUS301L steel was larger than that of SUS304, and the 0.2% proof stress and uniform elongation (U.El) were both similar for the two steels. The transformation rate and strength of martensite in the stress-induced martensitic transformation were compared by X-ray diffraction and Vickers hardness tests. At the same strain, SUS301L contained a larger volume fraction of martensite than did SUS304. Both steels showed similar values of the Vickers hardness. The difference between SUS301L and SUS304 is mainly due to the transformation rate of stress-induced martensite. The effects of the transformation rate and martensite strength on the TS/U.El balance in metastable austenite steels were demonstrated by means of the Weng secant method, based on a micromechanical model.