On the effect of intergranular nanocracks on the shear-coupled migration of tilt boundaries

in this work, we present molecular dynamics simulations of the shear-coupled migration behaviour of symmetrical tilt boundaries σ 17(530)/[001] perturbed by the presence of nanocracks lying on the grain boundary. the simulations were performed for copper bicrystals at 300 k. the focus has been on the study of crack size effects. the simulations were carried out using the embedded atom method with temperature control. systems of constant width, x, and different crack sizes, 2a, were generated at 0 k. the ratio 2a/x characterizes the system. periodic boundary conditions were set along the direction of application of the load and the tilt axis. after relaxation, the virtual shear of the bicrystals was carried out at a constant rate of 108 s-1. the response of the cracked specimens can be divided into: (i) shear-coupled migration of the grain boundary with increasing applied shear stress, (ii) intergranular propagation of the crack and (iii) emission of dislocations and closing of the grain boundary dislocation loop.