[SY-I5] Heterogeneous disconnections nucleation mechanisms during grain boundary migration
Invited
In specific conditions, grain boundary (GB) migration occurs in polycrystalline materials as an alternative vector of plasticity compared to the usual dislocation activity. The shear-coupled GB migration, the expected most efficient GB based mechanism, couples the GB motion to an applied shear stress. The migration of the GB occurs through the nucleation and motion of disconnections.
We report a detailed theoretical study of the elementary mechanisms occurring during heterogeneous disconnections nucleation. Using molecular simulations, the absorption of a $1/2[110]$ edge bulk dislocation in a symmetric $\Sigma{17}(410)$ $[001]$ tilt GB generates an immobile disconnection in the GB. We show that the shearing of this GB induces its migration and reveals a new GB migration mechanism through the nucleation of a mobile disconnection from the immobile one. Energy barriers and yield stress for the GB migrations are evaluated and compared to the migration of a perfect GB. As expected, the migration of imperfect GB is easier than the one of perfect GB. An immobile disconnection in a BG can thus operate as a source of disconnections driving the GB migration.
We report a detailed theoretical study of the elementary mechanisms occurring during heterogeneous disconnections nucleation. Using molecular simulations, the absorption of a $1/2[110]$ edge bulk dislocation in a symmetric $\Sigma{17}(410)$ $[001]$ tilt GB generates an immobile disconnection in the GB. We show that the shearing of this GB induces its migration and reveals a new GB migration mechanism through the nucleation of a mobile disconnection from the immobile one. Energy barriers and yield stress for the GB migrations are evaluated and compared to the migration of a perfect GB. As expected, the migration of imperfect GB is easier than the one of perfect GB. An immobile disconnection in a BG can thus operate as a source of disconnections driving the GB migration.