  The transition between necking-mediated tensile failure of glasses, at
elevated temperatures and/or low strain-rates, and shear-banding-mediated
tensile failure, at low temperatures and/or high strain-rates, is investigated
using tensile experiments on metallic glasses and atomistic simulations. We
experimentally and simulationally show that this transition occurs through a
sequence of macroscopic failure patterns, parametrized by the ultimate tensile
strength. Quantitatively analyzing the spatiotemporal dynamics preceding
failure, using large scale atomistic simulations corroborated by experimental
fractography, reveals how the collective evolution and mutual interaction of
shear-driven plasticity and dilation-driven void formation (cavitation) control
the various macroscopic failure modes. In particular, we find that at global
failure, the size of the largest cavity in the loading direction exhibits a
nonmonotonic dependence on the temperature at a fixed strain rate, which is
rationalized in terms of the interplay between shear- and dilation-driven
plasticity. We also find that the size of the largest cavity scales with the
cross-sectional area of the undeformed sample. These results shed light on
tensile failure of glasses, and highlight the need to develop elasto-plastic
constitutive models of glasses incorporating both shear- and dilation-driven
irreversible processes.
