Correlations among atomic mobility, microstructure and local stress of shear bands and necking regions in notched Cu50Zr50 metallic glasses

The atomic mobility, microstructure, and local stress in the shear bands and necking regions of notched Cu50Zr50 metallic glasses are compared, and the intricate interplay among them is examined via molecular dynamics simulations. The virtual tensile tests show that the average atomic mobility inside the mature shear band is lower than that in the necked region, which is controlled by the corresponding atomic-level structure. The short-range topological orders revealed by the Voronoi tessellation of both the necked region and the shear band are, however, quite similar to each other, while the excess free volume of the former is significantly higher than that of the latter. This high free volume content contributes to the migration of atoms or clusters and, thus, expedites the local plastic deformation. Further investigations suggest that the free volume content correlates closely with the local hydrostatic stress, while the topological microstructure is rather insensitive to the hydrostatic stress, especially when the hydrostatic stress is low. In addition, it is also found that the atomic mobility of the central atom in a cluster correlates not only with the local packing environment, such as the free volume content or the hydrostatic stress, but also with the geometry of the cluster, such as its symmetry or coordination number. The findings are helpful in developing/selecting the constitutive models for the deformation of metallic glasses.