Stability of stacking fault tetrahedron in twin boundary bicrystal copper under shear

Abstract

Stacking fault tetrahedrons (SFTs) appear nearly immobile in metals, its stability under shear loading is worth studying and discussion. In this paper, we present mechanism studies of SFT in twin boundary (CTB) bicrystal copper and single crystal copper under shear. Three different sizes of SFT and four different distances from SFT to CTB are considered. Detailed analysis of atomistic structures involved in CTB migration and SFT configuration evolutions during the shear are made. It is found that CTB bicrystal and single crystal embedded with a larger size of SFT have a smaller critical stress at their incipient plasticity. A complete transformation of SFT is assisted by dislocation motions and atomic diffusions in SFT area. Dislocation motion begins with the dissociation of two stair-rod dislocations on the SFT basal plane while the CTB migration direction with respect to SFT, resulting in the atomic diffusions, determines the final configuration of SFT. The continuous migrations of CTB towards and away SFT respectively lead to the collapse and flip over of SFT. This work, the first investigation of the stability of SFT in CTB bicrystal copper and single crystal copper under shear, may be helpful in revealing mechanical properties of irradiated metals.