Microstructure and mechanical properties of Fe–0.2C–5Mn steel processed by ART-annealing

Microstructure and mechanical properties of medium manganese steel (Fe–0.2C–5Mn) processed by annealing at 650 °C with annealing time up to 12 h after accelerated cooling were studied. It was found that the martensite structure was gradually transformed into a superfine ferrite and austenite duplex structure by austenite reverted transformation during annealing process. The annealing heat treatment results in a large volume fraction of austenite (34%) and an excellent combination of ultimate tensile strength (∼1000 MPa) and total elongation (>40%) at room temperature. The ultrahigh tensile strength and improved ductility of present steel were mainly attributed to the enhanced phase transformation induced plasticity due to the large fractioned austenite.