Tailoring the strength-ductility balance of a commercial austenitic stainless steel with combined TWIP and TRIP effects

The sequential twinning-induced plasticity (TWIP) and transformation-induced plasticity (TRIP) effects were induced in a commercial AISI 304L stainless steel by tailoring the average austenite grain size (via thermomechanical processing of cold rolling and reversion/recrystallization annealing), leading to a combination of high yield stress and total elongation as well as a remarkable strength-ductility synergy similar to advanced high-strength steels (AHSS) for automotive industry. In fact, the refinement of grains promoted the TWIP effect at the expense of the TRIP effect due to its effect on increasing the apparent stacking fault energy; while the coarsening/growth of grains led to a pronounced TRIP effect via deformation-induced martensitic phase transformation during straining. Moreover, the TRIP/TWIP effects were characterized by the simple work-hardening analysis such as slope change and appearance of extremum points on the curves of work-hardening rate, logarithmic and parabolic segments on the curves of instantaneous work-hardening exponent, and deviations from the strain-hardening Hollomon lines. The results were supported by the interrupted tensile tests and detailed electron backscattered diffraction (EBSD) analysis, where the merit of the TWIP-TRIP steels was shown in the case of a commercial austenitic stainless steel.