Microstructure and texture evolution of a high manganese TWIP steel during cryo-rolling

Abstract

The influence of rolling at 77K and 293K to a true strain of 2.66 on the microstructure and texture evolution and mechanical behavior of a TWIP Fe-0.3C-23Mn-1.5Al steel was quantified. The microstructure evolution at both temperatures of deformation was associated with an increase in the dislocation density and extensive twinning, following by the development of a cell structure and shear bands. Rolling at both temperatures was associated with a formation of the Copper-type texture in the beginning of deformation and transition to the Brass-type texture during further rolling. Intensive formation of ε-martensite was observed at 77K. The transformation of twin boundaries into arbitrary high-angle grain boundaries due to interaction with lattice dislocations led to the formation of grains/subgrains with the size of 30–60nm after cryo-rolling to a strain of 2.66. Rolling at both temperatures resulted in continuous increase of strength of the steel and decrease of ductility. The ultimate tensile strength was 1993MPa and 1824MPa after rolling to a true thickness strain of 2.66 at 77K and 293K, respectively. Qualitative analysis of contributions of different strengthening mechanisms was performed.