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Tracking the sliding of grain boundaries at the atomic scale

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. Description Pushing the grain boundaries The behavior of grain boundaries in metals during deformation is important because it can dictate the macroscopic behavior. Lihua et al. used aberration-corrected in situ electron microscopy observation of platinum grain boundaries during straining to detail how they evolve. The authors observed grain boundary sliding, which is a well-known and expected mechanism. However, the authors also observed a unexpected mechanism that involves the removal of lattice planes at the grain boundaries. Their observations show the importance of using very-high-resolution microscopy to understand the role of grain boundaries during deformation. —BG Electron microscopy shows that platinum grain boundaries evolve in unexpected ways during straining.