Molecular dynamics study of the interactions between dislocation and imperfect stacking fault tetrahedron in Cu

Abstract

The microstructure of irradiated face centered cubic alloys with low stacking fault energy is distinguished by the formation of a high number density of nanometer size stacking fault tetrahedra (SFT). A recent transmission electron microscopy investigation of high-energy proton irradiated copper [16] has shown that nearly 50% of the visible SFT population are not perfect SFTs, but rather consist of truncated SFT and/or groups of overlapping SFT. This paper presents the results of atomistic molecular dynamics simulations of the interaction between gliding dislocations, of either edge or screw character, and truncated SFT or overlapping SFT. The most common result of the edge dislocation interaction with a truncated SFT is defect shearing, ultimately leading to complete separation into two smaller defect clusters. Partial absorption of the truncated SFT is the most common result of the interaction with a screw dislocation, resulting in the formation of super-jog (or helical) segments as the defect is absorbed into the dislocation core. The resulting non-planar screw dislocation is self-pinned with reduced mobility and is re-emitted as a similar truncated SFT as the applied shear stress is increased. The re-emitted truncated SFT is often rotated and translated relative to the original position. These observations are consistent with the hypothesis that shearing (decreased defect cluster size) and dislocation dragging of the defect clusters by partial absorption into the dislocation core contributes to the formation of defect-free channels.