Ultra-flash annealing constructed heterogeneous austenitic stainless steel with excellent strength-ductility

The application of austenitic stainless steel is seriously restricted due to its relatively low yield strength. To significantly improve the strength of austenitic stainless steel with an acceptable decrease in ductility, the as-received austenitic stainless steel is cold-rolled with 90% thickness reduction to obtain the hybrid structures including retained austenite, deformation-induced martensite, and subgrains. Subsequently, an ultra-flash annealing strategy is proposed to produce the heterostructured austenitic stainless steel consisting of recrystal-lized austenite grains and non-recrystallized austenite zones (diffusionless-reversion formation), and the hybrid microstructure formed by ultra-flash annealing shows superior strength-ductility synergy. The thorough inves-tigation reveals that the origin of the high yield strength is not only grain boundary strengthening, but also the back-stress hardening induced by the constraint of hard domains to soft domains. The consequent high uniform elongation is provided by the synergistic effect of dislocation hardening, back-stress hardening and twinning, which is different from the coarse austenitic stainless steel with twinning-induced plasticity and transformation-induced plasticity.

Automated summary

This study investigates the methods and mechanisms to improve the strength of austenitic stainless steel. The hybrid structures of austenitic stainless steel are obtained through cold rolling and ultra-flash annealing, showing superior strength-ductility synergy.