Grain Boundary Shear-Migration Coupling in UFG Al Studied Using In Situ TEM and Other Advanced Methods

In small grained metals, the postulate that dislocation-based plasticity is shut-down at lower scales is often accompanied by the qualitative assertion that grain-boundary -based mechanisms are taking over. However, very few experimental evidence have quantified these mechanisms. Shear-coupling grain boundary for instance is a poorly known mechanism, that is only starting to be investigated. As grain boundaries possess many more degrees of liberty than dislocations, characterizing GB-based mechanism is complex. Here, we combined in situ TEM with digital image correlation (DIC), Automatic Crystallographic Orientation Mapping (ACOM), Electron Back Scattering Diffraction (EBSD) and Atomic Force Microscopy (AFM) to measure the extent of shear migration coupling mechanisms in an ultra-fine grain aluminum alloy. The results will be compared to the few existing models of this type of plasticity.