Distribution of dislocation-twin interaction in TWIP steel under different loading modes

Abstract

Twinning induced plasticity (TWIP) steel with nanotwinned structure enables it to have adjustable strength and elongation. However, the dislocation reactions at the twin boundary (TB) in nanotwinned materials have obvious tension-compression asymmetry and orientation effects, and the corresponding mechanism of dislocation-TB interactions is not yet fully understood. In this study, the tension-compression asymmetry and orientation effect of dislocation-TB interactions in twinned TWIP steel is investigated using the discrete dislocation dynamics simulations and Schmid's law. The different types of dislocations dominate the TB migration in the twinned TWIP steel during tension and compression with the same loading orientation, and the asymmetric dislocation reactions at TB are attributed to the different leading partials produced after the dissociation of dislocation under different loading modes (tension or compression). Moreover, the complex dislocation-TB interactions, such as dislocations traversing TB, cross slip, dissociation, pile up and so on, are determined by considering the orientation effect of dislocation activation and the asymmetry of dislocation dissociation. The research advances the understanding of asymmetric behavior of twin and its influence on the macro hardening in plastic deformation of TWIP steels.