Atomistic simulations were used to investigate dislocation nucleation from Σ3 asymmetrical (inclined) tilt grain boundaries under a uniaxial tension applied perpendicular to the boundary. Molecular dynamics was employed, based upon embedded atom method potentials for Cu and Al at 10 and 300K. The results included the grain boundary structure and energy, together with mechanical properties and mechanisms associated with dislocation nucleation from these Σ3 boundaries. The stress and work required for dislocation nucleation were calculated together with elastic stiffness of the bicrystal configurations, exploring the change in response as a function of inclination angle. Analyses of dislocation nucleation mechanisms for asymmetrical Σ3 boundaries in Cu showed that dislocation nucleation was preceded by dislocation dissociation from the boundary. Dislocations then preferentially nucleated in only one crystal on the maximum Schmid factor slip plane(s) for that crystal. However, this crystal was not simply predicted based upon either the Schmid or non-Schmid factors. The synthesis of these results provided a better understanding of the dislocation nucleation process in these faceted, dissociated grain boundaries.

Dislocation Nucleation in Σ3 Asymmetric Tilt Grain Boundaries. M.A.Tschopp, D.L.McDowell: International Journal of Plasticity, 2008, 24[2], 191-217