Atomic-scale observation of dynamic grain boundary structural transformation during shear-mediated migration

Area of Science:

• Materials Science
• Nanotechnology
• Physical Chemistry

Background:

• Stress-driven grain boundary (GB) migration is crucial in nanocrystalline materials.
• Atomic-scale mechanisms of GB structural change during migration remain experimentally underexplored.

Purpose of the Study:

• To investigate the dynamic atomic-scale structural transformations of grain boundaries during stress-driven migration.
• To elucidate the mechanisms of reversible facet transformation and GB dissociation.

Main Methods:

• In situ high-resolution transmission electron microscopy (HRTEM).
• Molecular dynamics (MD) simulations.
• Observation of shear-mediated migration in gold nanocrystals.

Main Results:

• Observed reversible transformation between (002)/(111) and Σ11(113) GB facets via GB steps.
• Identified GB dissociation into Σ11(113) and Σ3(111) facets through partial dislocation emission.
• Demonstrated that transformations are loading-dependent and influenced by GB junctions.

Conclusions:

• Provided atomistic insights into dynamic GB structural transformations during migration.
• Revealed reversible facet transformation and GB dissociation as key mechanisms.
• Highlighted the role of GB steps and junctions in mediating these processes.