Improving Ductility of a 3Mn Medium-Mn Steel by Manipulating the Austenite Reversion Path

In the present study, a simple but effective two-step annealing processing strategy via manipulating the austenite reversion path is proposed to obtain a large fraction of retained austenite in low-Mn medium-Mn steels. Initially, the Fe–3Mn–0.2C–1.5Si (wt%) steel is intercritically annealed to form Mn-enriched lamellar martensite precursors. Subsequently, the austenite reversion transformation is manipulated to occur within the martensite lamellae during the second annealing process, resulting in an ultra-fine duplex microstructure of laminated austenite and ferrite. This process can not only allow a large fraction of austenite to be retained in low-Mn medium-Mn steels, but also increase the elongation by up to 41% without sacrificing the strength level compared to the conventional annealing.