Atomistic Simulations of Stress Concentration and Dislocation Nucleation at Grain Boundaries

Dislocation channeling observed in irradiated metals has been thought to be one of the key stress factors in irradiation assisted stress corrosion cracking since it is an evidence to suggest that the slip deformation is localized and that the strong misfit are generated at grain boundaries. In the present study, the stress concentration and defect nucleation of polycrystalline copper thin film is investigated by parallel molecular statics simulations. Uniaxial tensile deformation is applied to the two-dimensional polycrystalline model. As a result, it is found that the stress concentration is observed at triple point of grain junctions in the elastic and initial stage of plastic deformation. Then partial dislocations are first generated from the small angle grain boundaries. Twin deformations occur at triple points and grain boundaries which result in both another site of stress concentration around grain boundaries and local displacement relevant to the Burgers vector at grain boundary. One distinguishing characteristic of deformation mode of polycrystal is that the stress distribution strongly correlated with the presence of the partial dislocations and twin boundaries. Stress relaxation within each grain is preferentially brought about by the dislocation nucleation and twin deformation.