In situ TEM and multiscale study of dislocation loop formation in the vicinity of a grain boundary

Preferential formation of dislocation loops near a grain boundary (GB) in pure magnesium was observed under in-situ TEM 200 KV electron irradiation at 300 K. These loops are vacancy in nature. A rate-theory-based model is presented to explain this observation. Specifically, the model considered an irradiated domain surrounded by GBs and free surfaces. Molecular dynamics (MD) and finite difference methods (FDM) were combined to calibrate and solve the model. The distribution of loops with respect to the GB can be divided into three regions: 1) a defect free zone adjacent to the GB, 2) a region with vacancy loops in the distance range of 10–200 nm from the GB, and 3) a region free of extended defects far away from the GB. The characteristics of the three zones, and the vacancy nature of the loops can be explained by the relative sink strength of the GB to interstitial-type and vacancy-type defects. [Display omitted]