| Abstract Scope |
Warm rolling has recently received more attention in making high-performance steel sheets. In this work, we demonstrate a warm rolled medium Mn steel (WR) compared with one fabricated by intercritical annealing (IA). Instead of low- dislocated and equiaxed grains from intercritical annealing, the WR steel has an elongated prior austenite microstructure with alternating ferrite-rich and -poor regions. Compared with IA steel, the WR steel has higher yield stress attributed to a higher dislocation density and persistent work hardening due to continuous TRIP effect. After hydrogen charging, both steels are degraded by hydrogen-assisted cracks because of the HEDE mechanism. Multiple crack initiations are observed in both steels, which are primarily perpendicular to the loading direction in the IA steel while deflected by PAGB and ferrite/martensite boundaries in ferrite-rich regions in the WR steel. The crack deflections contribute to the improved hydrogen embrittlement resistance of the WR steel. |