In situ atomistic observations of dynamics of Lomer dislocations in Au subjected to electron-beam irradiation

Abstract

Electron-beam-induced dynamics of Lomer (L) dislocations in an Au low-angle grain boundary (LAGB) was captured in situ at the atomic scale with a transmission electron microscope (TEM). Under electron-beam irradiation, L dislocations dissociated into the Lomer-Cottrell (LC) configuration or into a combination of a Frank partial dislocation and a Shockley partial dislocation (SPD), and these configurations underwent the mutual transition. The LAGB contained a step dislocation, likely resulting from an inherent GB inclination. This dislocation was either a 60° dislocation or a pair of SPDs (30° and 90°). Under prolonged electron-beam irradiation, the step dislocation and the other dislocations in the LAGB reversed their order. This transposition occurred by the decomposition of the L dislocations and their dissociation products into their parent dislocations (60° dislocations or pairs of SPDs) and the subsequent combination of a decomposition component and the step dislocation. The decomposition and combination relocated the step dislocation, resulting in a stepwise migration of the LAGB. The decomposition was attributed to interdislocation forces due to neighboring dislocations in the LAGB, which were facilitated by electron-beam heating via inelastic scattering of incident electrons and external forcing through electron-beam irradiation.