Serration Dynamics in a Zr-Based Bulk Metallic Glass

Intermittent or serrated plastic flows have been widely observed in irreversible deformation through shear banding in bulk metallic glasses (BMGs). The strain-rate-dependent plasticity under uniaxial compression at 2 x 10(-3), 2 x 10(-4), and 2 x 10(-5) s(-1) in a Zr-based BMG is investigated. Serration events have a typical time scale at a relatively higher strain rate (2 x 10(-3) s(-1)), while at lower strain rates, there is a lack of typical time scale. During serrations, the stress is falling rapidly, and the amplitude of the stress drop between the neighboring serrations is approximately equal. The stress drop vs time satisfies the exponential decay rule during jerk flows. Due to the serrated flow corresponding to the internal shear process, the free-volume model and stick-slip model are introduced to explain how the shear bands form and propagate and the cooperation of multiple shear bands. The mechanism is explained by relating the atomic-scale deformation with the macroscopic shear-band behavior, offering key ingredients to fundamentally cognize serrations in jerk flows.