In situ atomic-scale observation of diffusion-assisted pure sliding of coherent twin boundary in Pt

Abstract

Coherent twin boundary (CTB) can markedly enhance the strength of metallic materials because thermally stable CTBs act as strong barriers for blocking dislocation motion. CTB sliding should rarely happen because twinning dislocations (TDs) nucleate with a lower activation energy than a full dislocation while the gliding of TDs migrates the CTB. Here, the atomic-scale sliding process of CTB was in situ captured in a twin-structured Pt, involving two TDs that glide toward each other on two non-coplanar (111) planes separated by the CTB. They meet and then exchange their sliding planes assisted by short-range atomic diffusion to continue gliding, resulting in pure sliding across the CTB without migration of the CTB. Repeat of this pure sliding process requires the assistance of atoms diffusion to annihilate the created vacancies. This sliding mechanism enriches CTB-related plastic deformation mechanisms.