Yield point of metallic glass

Li, J.*; Shimizu, Futoshi ; Ogata, Shigenobu*

Shear bands form in most bulk metallic glasses (BMGs) within a narrow range of uniaxial strain 2%. We propose this critical condition corresponds to embryonic shear band (ESB) propagation, not its nucleation. To propagate an embryonic shear band, the far-field shear stress must exceed the quasi steady-state glue traction of shear-alienated glass until the glass-transition temperature is approached internally due to frictional heating, at which point ESB matures as a runaway shear crack. The incubation lengthscale necessary for this maturation is estimated to be 10nm for Zr-based BMGs, below which sample size-scale shear localization does not happen. We model 4 metallic glasses: a binary Lennard-Jones system, two binary embedded-atom (EAM) potential systems, and a quinternary EAM system. Despite vast differences in the structure and interatomic interactions, the four MD calculations give yield strain predictions of 2.4%, 2.1%, 2.6% and 2.9%, respectively.