Atomic force microscopy reveals thermally induced grain growth via shear-coupled migration

Grain boundary (GB) migration is typically assumed to proceed by diffusive atomic events following curvature-driven flow. However, recent 4D (3D plus time) experiments and atomic-to-mesoscale simulations have shown that thermally induced grain growth in polycrystals deviates from this assumption. GB migration mediated by disconnections—producing both boundary translation and shear—may resolve this discrepancy, although such shear is usually restricted by surrounding grains. We directly demonstrate shear-coupled migration during grain growth in [Formula: see text]m-sized nickel by measuring surface displacements associated with GB migration using atomic force microscopy. Migrated GBs induced significant surface topography changes, clearly differing from grooves observed for stationary GBs.