Twinning activities in high-Mn austenitic steels under high-velocity compressive loading

High-velocity compression tests were carried out on three different types of high-manganese (Mn) austenitic steels, namely Hadfield, TWIP and XIP steels, with the purpose of favoring twinning over slip. The experiments were conducted at three temperatures: −170°C, room temperature and 200°C, in order to cover both ductile and brittle deformation ranges. Various mechanisms such as slip, formation of more than one twin variant, nano-twins inside primary twins and voids were activated in Hadfield steel, while the deformation was twin-dominated in TWIP steel at all temperatures, which stems from the increase in stacking fault energy (SFE) due to the higher Mn content. The XIP steel with the highest SFE, on the other hand, deformed mostly by slip at elevated temperatures, even though extensive twin and nano-twin formation was prevalent in the microstructure as the temperature decreased to room temperature, and then to −170°C, respectively. The current set of results lay out the roles of temperature, deformation velocity and alloy content on the microstructure evolution of high-Mn steels, which altogether can be tailored to improve the work hardening capacity of this class of materials.