Plasticity enhancement and sustainable strain hardening mechanism of a novel developed medium Mn steel

A novel medium manganese steel denoted as Fe-8Mn-0.3C-1.5Si-3Al-0.2Nb (wt.%) is developed via the combination of two-stage warm rolling (TWR) and intercritical annealing (IA), which exhibits excellent strength and elongation of 1203 MPa and 47.2 %, respectively. The sustainable strain hardening and plasticity enhancement in the scenarios of various IA treatments are elaborated via the analysis of TRIP-assisted deformation and fracture mechanisms. It is indicated that the combination of the continuous/discontinuous TRIP effect and the dynamic balance between dislocation pile-ups and annihilation contribute to the sustainable strain hardening. The excellent plasticity is attributed to TRIP effect, plenty of deep/fine dimples and few cracks.