Interplay between dislocation type and local structure in dislocation-twin boundary reactions in Cu

Dislocation-twin boundary interactions in Cu are systematically studied using molecular dynamics simulations. Specifically, interactions between screw dislocations and 60\ifmmode^\circ\else\textdegree\fi{} mixed dislocations with both coherent and incoherent twin boundaries are examined. Importantly, the study considers both metastable and minimum-energy configurations of these twin boundaries to explore the impact of local atomic arrangements on dislocation-twin boundary interactions. The results indeed reveal two distinct mechanisms for dislocation transmission through twin boundaries: partial dislocation reaction versus full dislocation absorption followed by emission in the adjacent grain. The observed interaction mechanisms are found to be similar in the case of other symmetric tilt GBs with similar local structural units. Therefore, the interplay between dislocation type and grain boundary (GB) structure can strongly influence the transmission of dislocations across GBs. Even a subtle change of approximately 1.5% in the nearest-neighbor distance of the coherent twin boundary (metastable vs minimum-energy structure) alters the outcome of the dislocation-twin boundary interaction (transmission vs absorption). Specifically, the screw dislocation can transmit through metastable but not the minimum-energy coherent twin boundary. This further highlights the important role of GB structure, especially those metastable structures, in material strength modeling.