The interaction, with an asymmetrical tilt grain boundary, of a dislocation array which was emitted from a crack tip under mode-II loading conditions, was analyzed. The grain boundaries could be characterized by planar and linear matching zones or non-matching zones. It was observed that all of the grain boundaries emitted dislocations. The boundaries migrated easily, due to their planar and linear matching structure and asymmetrical nature. The diffusion which was promoted by stress concentrations was found to aid boundary migration. Transmission of dislocations occurred either along the matched plane or along another plane; depending upon the tilt angle. Alternating processes of stress concentration and stress relaxation occurred ahead of the pile-up. The stress concentration could be relaxed by dislocation transmission, by atom diffusion along grain boundaries, or by migration via the formation of twinning bands. The simulations demonstrated that asymmetrical boundaries evolved into symmetrical ones, and that non-matching zones evolved into matching ones, during loading.

Molecular Dynamics Simulation of the Interaction of a Dislocation Array from a Crack Tip with Grain Boundaries. Y.W.Zhang, T.C.Wang: Modelling and Simulation in Materials Science and Engineering, 1996, 4[2], 231-44