Coupling nano-carbide strengthening with transformation induced plasticity effect to achieve over 1.5 GPa strength with 30% ductility in cold-rolled medium-Mn steel

An ultra-high strength (over 1500 MPa) and enhanced ductility (30%) of cold-rolled medium-Mn steel is developed by quenching and tempering heat treatment. The highest product of strength and elongation of 45.7 GPa·% is obtained when tempering at 300 °C. The microstructure consists of martensite matirx, substantial nano-carbide and film-like/blocky retained austenite. The ultra-high strength derives from the precipitate strengthening of nano-carbide as efficient obstacles to dislocation motion. While, transformation induced plasticity effect of retained austenite enhances the plasticity.