STZ-Vortex model: The key to understand STZ percolation and shear banding in metallic glasses

The fast dynamics and localized nature of shear banding together with the disordered structure of metallic glasses make it difficult to gain an understanding of the mechanism of strain localization and shear band formation during deformation. The most widely accepted theory for the atomic-scale mechanisms of shear banding is related to the percolation of shear transformation zones (STZs). Recently we reassessed and clarified the atomistic details of STZs self-assembly mechanisms and provided a new two-unit model crucial in understanding STZs percolation and shear band formation. This manuscript attempts to provide a brief but up-to-date review on the STZ-Vortex mechanism and its applications in the areas of the shear band dynamics and, in general, in the atomistic description of deformation mechanisms in metallic glasses. The review also identifies a number of unsolved issues concerning deformation and relaxation mechanisms in metallic glasses where the STZ-Vortex model could be successfully applied.