The migration kinetics of coherent twin boundaries and the underlying atomistic mechanisms were determined through molecular dynamics computer simulations. Details of motion dynamics and associated effective migration of coherent twin boundaries were examined for nanotwinned copper crystals under externally applied shear loading. The present study reveals that the magnitude and direction of the resulting coherent twin boundary migration velocity was dependent on the shear-loading orientation. It was found that <112>-type shearing on {111} twin boundaries maximizes their transverse migration velocity. Shearing at directions which remain parallel the twin boundary plane but were inclined to the <112>-direction results in a smaller degree of coupling, and finally to twin boundary sliding alone when the shear direction was along <110>. It was found that the dynamics of coherent twin boundary motion could be described as a two-step “stick–slip” process. Analysis of atomic configurations indicates that the “stick” phase of the dynamics was associated with accumulated strain in the crystal, and that such strain was suddenly released by the nucleation of 1/6 [112]-type twinning partial dislocations. In atomic layers adjacent to the twin boundary, coordinated shuffling of atoms was found to take place immediately before dislocation nucleation. The so-called slip phase of the dynamics was shown to be controlled by fast propagation of nucleated twinning partial dislocations and their spreading along the twin boundary.

Stick–Slip Dynamics of Coherent Twin Boundaries in Copper. Q.Hu, L.Li, N.M.Ghoniem: Acta Materialia, 2009, 57[16], 4866-73