Effects of Rolling Temperature on the Microstructure and Mechanical Properties of a High-Mn Austenitic Steel for Cryogenic Applications

The effects of rolling temperature on the microstructure and mechanical properties of a high-Mn austenitic steel is investigated. It is observed that the grain size decreases with the decrease in rolling temperature, resulting in an increase in yield strength (YS) and an increase in ultimate tensile strength (UTS). Mechanical twinning is found to be less active in fine-grained specimen, leading to the decrease in uniform and total elongations and impact toughness. The existence of dislocations and nanoscale mechanical twins in the initial microstructure contributes to the high YS, and the active mechanical twinning during deformation maintains excellent ductility and impact toughness. The thick twins (generally thicker than 300 nm and formed during hot rolling) play a supplementary role in increasing the instantaneous strain hardening during the late stage of tensile deformation.