The effect of extrinsic grain-boundary dislocations in non-equilibrium grain boundaries upon the mechanical properties of ultrafine-grained metals was investigated by molecular dynamics simulations. Aluminium bicrystal models containing cracks and extrinsic grain-boundary dislocations impinging from the crack tips were prepared. First, the dependence of the local grain boundary structure upon the accommodation mechanism of extrinsic grain-boundary dislocations, and upon its stress field was studied. Then, the shielding effect of extrinsic grain-boundary dislocations upon the emissions of dislocations from crack tips was investigated, and the effect of non-equilibrium grain boundaries upon the intragranular deformation was considered. Finally, to investigate the relationship between extrinsic grain-boundary dislocations and intergranular deformations, shear loading was applied to the bicrystal models. It was found that extrinsic grain boundaries function as the intergranular deformation source, and the Burgers vector components of the extrinsic grain-boundary dislocations led to anisotropic grain boundary sliding.

Effect of Extrinsic Grain Boundary Dislocations on Mechanical Properties of Ultrafine-Grained Metals by Molecular Dynamics Simulations. T.Shimokawa, T.Hiramoto, T.Kinari, S.Shintaku: Materials Transactions, 2009, 50[1], 2-10