Direct observation and quantification of grain boundary shear-migration coupling in polycrystalline Al

Rapid grain boundary motion under stress has been observed during in-situ TEM straining experiment in polycrystalline Al at moderate temperatures. Crystallographic orientation of both sides of moving grain boundaries (GBs) was simultaneously recorded. A shear produced by the grain boundary migration has been estimated using fiducial markers and image correlation yielding a coupling factor (i.e., ratio of the shear strain over the migration distance) of around 7%. This result is compared to existing models based on shear coupled migration theories, and is discussed within the new Shear Migration Geometrical model (SMIG).