The excellent strength and ductility matching of directly warm-rolled V-alloyed medium manganese steel by stacking fault networks

A V-alloyed medium manganese steel with the yield strength of 1107 MPa, tensile strength of 1231 MPa and total elongation of 44.5 % was obtained directly by warm rolling. It is clarified that the high density of dislocations, stacking fault networks, Lomer-Cottrell (L-C) locks and nano-precipitates in the worm-rolled austenite play important roles for the ultrahigh yield strength. The spacing of the stacking faults gradually decreases and the density of L-C locks increases simultaneously during the tensile deformation, resulting in the dynamic refinement of stacking fault networks, which can effectively hinder the movement of dislocations. Thus, the continuous work-hardening ability and excellent total elongation at the ultrahigh yield strength are caused by the combined contribution from the dynamic Hall-Petch effect of stacking fault networks, the dispersed nano-precipitates and the partial TRIP effect. Our results open the way for designing stacking fault- and precipitation-strengthened medium manganese steel with advanced strength, ductility and work-hardening combination.