Effect of cryogenic deformation on microstructure and mechanical properties of 304 austenitic stainless steel

304 austenitic stainless steel plates have been deformed (10 to 40%) by multi-pass cold rolling incorporating soaking at 0 degrees C and -196 degrees C after each pass with an aim to correlate the microstructure and mechanical properties under cold/cryogenically deformed conditions. Characterisation of phase constituents, microstructure and mechanical properties of such steel specimens has been conducted after processing under different schedules. Rolling of the investigated steel at near cryogenic temperature results into the formation of extended stacking faults, epsilon-martensite and alpha'-martensite in contrast to the formation of homogeneous dislocation structure along with alpha'-martensite in the samples rolled at 0 degrees C, which can be correlated with temperature dependent stacking fault energy. EBSD phase analysis reveals 46.3% and 69.2% alpha'-martensite in the austenitic matrix for 10% and 20% deformation at -196 degrees C, respectively. Deformation twins are evident in all the samples rolled at 0 degrees C as well as 196 degrees C. 40% cold deformation at 0 degrees C leads to high strength (1225 MPa) and 13% total elongation, whereas comparatively lower 10-20% deformation at 196 degrees C leads to higher level of strength (1306-1589 MPa) with 15-9% elongation due to the formation of the higher volume fraction of strain induced martensite (epsilon/alpha').