The role of twinning on microstructure and mechanical response of severely deformed single crystals of high-manganese austenitic steel

► Two methods were used to produce an ultrafine-grained structure in high-Mn steel. ► Multiple twinning is responsible for the creation of an ultrafine-grained structure. ► The multistage growth of microhardness with strain correlates with deformation mode. ► A significant strengthening factor is the internal twinning of twins and shear bands.