Shear response of grain boundary bicrystals with a stacking fault tetrahedron

Abstract

Stacking fault tetrahedrons (SFTs) are commonly seen in the polycrystalline and nanocrystalline materials due to the heavy plastic deformation, quenching and irradiation. In this study, we present the transformation of SFT near four Cu symmetric tilt grain boundaries (GBs) under shear. Atomistic structures involved in GB deformation and SFT configuration evolutions during the shear are analyzed. Our results show that the presence of SFT has small influence on critical stress corresponding to the incipient plasticity of GB bicrystal. Because GB deformation such as migration, sliding and structure evolvement occur at a smaller external shear stress not large enough to activate the destroy of SFT, and SFT near four GBs transforms only when interacting with partial dislocation or GB. Besides, the presence of an SFT does not substantially change the deformation modes of these four GBs. Of one particular case is GB deforming in the complex mechanism due to atom-shuffling, partial dislocation nucleation and local GB dissociations. Significant stress concentration arises around GB due to SFT, which may change the nucleation site of partial dislocations.