Ultrafine wear-resistant TWIP steel via severe plastic deformation

This study evaluated the effect of severe plastic deformation via high-pressure torsion (HPT) on the microstructure and mechanical properties of Fe-23Mn-0.5 C (wt%) twinning-induced plasticity (TWIP) steel. The annealed steel was subjected to HPT at a pressure of 6 GPa and 30 turns of rotation. Following deformation, some discs were annealed at 673 K for 1 hour. The microstructures were examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Severe plastic deformation resulted in a substantial reduction in austenite grain size, along with the formation of epsilon-martensite, indicating the activation of the transformation-induced plasticity (TRIP) effect. Consequently, the hardness increased by nearly 300 %, the coefficient of friction (CoF) decreased, and the wear volume loss was reduced by over four-fold compared to the initial steel. The annealing of the HPT-processed material led to a slight softening due to recrystallization and reverse martensitic phase transformation. However, this thermal treatment resulted in the formation of nano- twins coupled with fine recrystallized grains which kept wear resistance at the same level.