Thermally activated nature of synchro-Shockley dislocations in Laves phases

Abstract

The synchro-Shockley dislocation, as a zonal dislocation, is the major carrier of plastic deformation in Laves phases at high temperatures. The motion of synchro-Shockley dislocations is composed of localized transition events such as kink-pair nucleation, propagation and short-range atomic shuffling. These events possess small activation volumes, presumably leading to sensitive temperature and strain rate dependence on the Peierls stress. However, the thermally activated nature of synchro-Shockley dislocations is not fully understood so far. In this study, the transition mechanisms of the rate-limiting steps of the motion of synchro-Shockley dislocations at different shear strain levels are studied. The transition processes of dislocation motion can be divided into shear-sensitive and -insensitive events. The external shear strain lowers the energy barriers of shearsensitive events. Thermal assistance is indispensable in activating shear-insensitive events, implying that the motion of synchro-Shockley dislocations is prohibited at low temperatures. We aim to advance the understanding of the mechanisms of motion of zonal dislocations in complex crystals.