Atomic-scale computer simulation of the hexagonal close-packed a-phase was used to investigate the mobility of interfacial defects in response to an applied shear stress. Interfacial defects in (10▪2) twins and a 90º incommensurate tilt boundary were investigated. Defects with their Burgers vectors parallel to the host interface could move conservatively, in principle, but were found to be mobile only if their step height was small. In such cases, especially when the defects had wide cores, the atomic shuffles which were involved in transferring atoms from the sites of one crystal to the other were simple. On the other hand, defects which exhibited large step heights usually had narrow cores and required complex shuffles for motion. An applied stress tended to cause core reconstruction and the emission of partial dislocations trailing stacking faults from these defects. Defects with Burgers vectors which were inclined to the interface could move conservatively in some circumstances, in response to an applied shear stress, via a climb-compensated mechanism. This mechanism could lead to a limited mobility of defects in both types of interface studied, and involved the generation of additional glissile interfacial defects; due to the stress-concentrating effect of the riser of the initial defects. The activation of this mechanism was feasible only when the elementary mechanism of motion involved a small number of atoms which shuffled from one crystal to the other. Unlike the case for defects with the Burgers vector parallel to the interface, this number was not simply related to the step height and could effectively be small even when the step height was relatively large.

Dislocations in Interfaces in the HCP Metals II. Mechanisms of Defect Mobility under Stress. R.C.Pond, A.Serra, D.J.Bacon: Acta Materialia, 1999, 47[5], 1441-53