AN ALMOST UNIFYING THEORY FOR GRAIN BOUNDARY-BASED PLASTICITY

摘要

Revealed in metallic nanocrystals, or thin films (Fig. 1) grain boundary (GB)-based plasticity has been studied for many years under various names: stress-assisted grain growth, grain rotation, grain boundary sliding or shear-coupled grain boundary migration. Based on MD simulations, TEM and in-situ TEM approaches, we will show that a key player in these mechanisms is the disconnection. This defect combines a step and a Burgers vector character, and belongs to GBs, especially real GBs. The motion of these defects can explain most of the above-mentioned mechanisms depending on the amplitude of both its step and dislocation components. But not all of them. Some observations suggest that local atomic shuffling also plays a role as clear non-conservative behaviours are detected, probably postponing the expected happy ending of a complete GB-based plasticity understanding.