| Abstract Scope |
Grain-boundary deformation plays a central role in the plasticity of fine-grained and nanocrystalline metals, yet the atomistic mechanisms governing asymmetric non-CSL boundaries remain incompletely understood. Here, we combine atomistic simulations with machine-learning potentials to investigate stress-driven interfacial deformation in asymmetric FCC grain boundaries, including both boundary sliding and disconnection-mediated migration. For sliding-dominated boundaries, the translation periodicity is governed by intrinsic grain-boundary dislocations, while the displacement-shift complete is dictated by the lattice periodicity of the flat close-packed {111} grain surface. Non-uniform sliding occurs through the glide of extrinsic grain-boundary dislocations that dissociate into fractional partials. In contrast, migration of these structurally complex boundaries requires coupled disconnection motion and non-conservative climb or rearrangement of intrinsic grain-boundary dislocations. These results reveal how intrinsic and extrinsic interfacial defects collectively control stress-driven deformation of asymmetric grain boundaries. |