Large deformation behavior of twin-induced plasticity steels under high-pressure torsion

Abstract

A high-manganese twinning-induced plasticity (TWIP) steel is processed by high-pressure torsion (HPT) for up to 1 turn under 6 GPa pressure. The HPT-processed TWIP steels exhibit a homogeneous microstructure with a peak hardness of Hv 550. Deformation twinning is developed significantly in the early stage of the shear deformation, but is exhausted soon after 1/2 turn. The strength of the HPT-processed TWIP steel significantly increased due to the accumulation of dislocations, but elongation dramatically decreased due to a lack of dislocations available for plastic deformations. An analysis of the evolution of strength by imposed large strain under high pressure suggests that strain hardening due to dislocation and twinning is exhausted in the early stages of the HPT process. Further strategy for enhancing both strength and ductility is proposed.