Effect of twin thickness on the resistance of dislocations to pass through the twin interfaces:

Abstract

The presence of coherent twin boundary (TB) in polycrystalline materials results simultaneous ultrahigh strength and ductility by controlling the deformation behavior with grown-in nano-twins and mechanical twinning. In twinning-induced plasticity (TWIP) steels, deformation twins are reported to nucleate at grain boundaries and grow in the thickness direction during tensile deformation, resulting in high work hardening due to the dynamic microstructure changes. The mean free path of dislocations in the matrix reduces by increasing the number of newly formed deformation twins as these are considered to be strong obstacles to dislocation glide. The interaction of dislocation with TBs has great importance in achieving optimum materials prosperities; however, the influence of the deformation twin thickness on deformation mechanism in TWIP steels has not yet been understood. In this study, in order to understand the impact of deformation twin thickness on the material strength, we investigate the interaction of 60 degrees lattice dislocations with deformation twins with different thicknesses in the matrix of Cu with lower stacking fault energy through molecular dynamics (MD) simulations and find an optimum twin thickness of strength in the systems. Finally, we propose a new type of size-dependent strengthening mechanism in TWIP steels.