In-situ atomic-scale observation the escape of irradiation-induced dislocation loops in magnesium

Abstract

The formation of dislocations or dislocation loops in irradiated materials significantly alters the physical and mechanical properties of the materials. In this research, by applying in situ high-resolution transmission electron microscopy techniques, the dynamics of dislocation and self-interstitial atom (SIA) loops in magnesium (Mg) under electron beam (e-beam) irradiation at the atomic scale were observed directly. The structural characteristics of dislocation and dislocation loops were investigated with transmission electron microscopy. The in situ atomic-scale observation demonstrated that the edged dislocation gradually grew along the [1¯100] direction, while the SIA loop shrank along the same direction and eventually disappeared. The proposed processes resulted from the climbing of the dislocation and dislocation loops, which was related to the e-beam-induced anisotropic diffusion of the Mg atoms in the vicinity of the dislocations or dislocation loops. Significantly, only one side of the SIA loop near the thinner area was observed to shrink during the whole escape process, namely, a pinning phenomenon. The relevant mechanisms are discussed. The results present the detailed escape process of SIA dislocation loops at unprecedented resolution, and these results provide a significant insight into the advancement of irradiation resistance of materials.