Atomistic simulations of correlations between volumetric change and shear softening in amorphous metals

In this paper we investigate atomic volume change and the quantitative correlations between the volume changes and shear softening in a model amorphous metal subjected to shear deformation. From extensive atomistic modeling, we show that the local volumetric change or free volume does occur during the deformation process, even at low strains; and plastic deformation sets in at a critical amount of free volume. A direct consequence of the local atomic volume change is the decrease of the local shear modulus of the amorphous metal. Shear banding or shear localization is, therefore, a result of the volume-expansion-induced mechanical softening.