Stress-Induced Martensitic Transformation Behaviors at Various Temperatures and Their TRIP Effects in SUS304 Metastable Austenitic Stainless Steel

The effect of temperature on the static tensile properties of the metastable austenitic steel JIS-SUS304 was investigated to clarify the conditions of stress-induced martensitic transformation behavior for maximum uniform elongation. Results of the static tensile tests showed that the tensile strength increased with decreasing temperature and that uniform elongation reached a maximum value at 308 K. The inverse temperature dependence of 0.2 % proof stress was observed below 243 K. The volume fraction of martensite increased with decreasing deformation temperature. The conditions under which the stress-induced transformation resulted in the maximum uniform elongation due to the transformation-induced plasticity (TRIP) effect in SUS304 steel were summarized in terms of the martensite volume fraction and rate of transformation. The martensite volume fraction at true strain, which indicates the maximum transformation rate, was found to be approximately 35% independent of the deformation temperature. In stress-strain relationships for which the maximum uniform elongation was obtained, both the evolution rate of the dislocation density and the work-hardening continued to increase until near-uniform elongation was observed, and the maximum calculated value of work-hardening was almost 20 MPa/%.