Grain boundaries (GBs) play an important role in the mechanical behavior of polycrystalline materials. Despite decades of investigation, the atomic-scale dynamic processes of GB deformation remain elusive, particularly for the GBs in polycrystals, which are commonly of the asymmetric and general type. We conducted an in situ atomic-resolution study to reveal how sliding-dominant deformation is accomplished at general tilt GBs in platinum bicrystals. We observed either direct atomic-scale sliding along the GB or sliding with atom transfer across the boundary plane. The latter sliding process was mediated by movements of disconnections that enabled the transport of GB atoms, leading to a previously unrecognized mode of coupled GB sliding and atomic plane transfer. These results enable an atomic-scale understanding of how general GBs slide in polycrystalline materials.

In this study, the deformation mechanisms of bent Si nanowires are investigated at the atomic scale with bending strain up to 12.8%. The sign and magnitude of the applied strain are found to govern their deformation mechanisms, in which the dislocation types (full or partial dislocations) can be affected by the sign (tensile or compressive) and magnitude of the applied strain. In the early stages of bending, plastic deformation is controlled by 60° full dislocations. As the bending increases, Lomer dislocations can be frequently observed. When the strain increases to a significant level, 90° partial dislocations induced from the tensile surfaces of the bent nanowires are observed. This study provides a deeper understanding of the effect of the sign and magnitude of the bending strain on the deformation mechanisms in bent Si nanowires.

In situ atomic-scale bending tests of twin-structured Ni nanowires were realised using a homemade deformation device. The results showed that the plastic deformation mechanism in twin-structured Ni nanowires depended on the deformation stage. At the early stages of bending deformation, the plasticity of twin-structured Ni nanowires was controlled by dislocations interacting with the twin boundaries or parallel to them. With increasing bending strain, both dislocation and face-centred cubic–body-centred tetragonal phase transition occurred. At very high bending strain, grain boundaries resulting from the lattice distortion/collapse were formed. This study details the deformation mechanisms of the twin-structured Ni nanowires under bending deformation, which advances the basic understanding of the plasticity mechanisms in metals.