Repulsive force between screw dislocation and coherent twin boundary in aluminum and copper

Molecular dynamics (MD) simulations in combination with an atomistic path technique are used to examine energies required to impinge a screw dislocation on a coherent twin boundary (CTB) in Al and Cu. At large distances, we find that the dislocation-CTB interaction is characterized by repulsive forces which can be attributed to both the elasticity mismatch and distortion (shift and rotation) of deformation fields across the twin boundary. The repulsive forces are determined as a function of distance between the dislocation and the twin boundary based on our MD data and the classical dislocation theory. At short distances, the interaction is significantly influenced by the shear strength of the CTB: relatively low CTB shear strength can induce close-range attractive forces and cause slip to be absorbed into the twin plane.