Novel 1.4 GPa-strength medium-Mn steel with uncompromised high ductility

A Fe-8.9Mn-1.59Si-1.0A1-0.25C medium-Mn steel was designed, and lath-like recovered martensite and reversed austenite were mainly obtained due to 20% reduction ratio during cold-rolling to avoid recrystallization during annealing. Ultimate tensile strength (UTS), total elongation (TE) and product of strength and elongation (PSE) achieve 1405 MPa, 41.0% and 57.6 GPa%, respectively. Desired continuous yielding is implemented. Multiple strengthening and ductility-enhancing mechanisms including transformation-induced plasticity (TRIP) effect, twinning-induced plasticity (TWIP) effect and dislocation strengthening contribute to the combination of ultrahigh-strength and uncompromised-ductility. Besides, the present steel has some advantages in manufacturing and welding due to the moderate-level carbon equivalent (CE).