| Abstract Scope |
Grain boundary sliding (GBS) is a fundamental mechanism that significantly influences the mechanical behavior and plastic deformation of polycrystalline metals, affecting a wide range of processes, including creep, grain rotation, and superplasticity. Despite decades of research, the dominant mechanisms underlying GBS remain elusive. This study investigates atomic-scale GBS mechanisms by combining in situ high resolution TEM experiments and atomistic simulations via transition state theory and nudged elastic band calculations. A dislocation-based model is developed to describe the GB superlattice, where intrinsic GB dislocations accommodate grain misorientation and misfit, while extrinsic GB dislocations govern the GBS. This model reveals that GBS proceeds through motions of extrinsic partial GB dislocations, which glide in a periodic manner, significantly differing from lattice dislocations. Additionally, the atomistically determined activation barriers and activation volumes of GBS are compared with experimental measurements. The findings provide new insights into the atomic-scale mechanisms of GB dynamics in nanocrystalline metals. |