Serrated flow kinetics in a Zr-based bulk metallic glass

At different strain rates, the stress-flow serrations in the compressive stress-time curves of a Zr-based bulk metallic glass (BMG) exhibit different magnitudes and time scales. A critical strain rate can be identified, at which the serrated flow kinetics is characterized to be homogeneous in both time and magnitude. Below the critical strain rate, the serrations are lack of homogeneous magnitudes and time scales because the excessive elastic energy results in distinct softening within the viscous fluid-like shearing layer due to the adiabatic heating. As a consequence, the tiny disturbances, such as the vibration of test machines, affect the shear banding behavior. A periodic function is established for the critical instability, and two pertinent parameters, the mean stress drop magnitude and the mean waiting time (MWT), can be determined, which may be associated with the deformation micromechanism, the mechanical property, and the glass-forming ability of BMGs. The present approach may provide a new way to study the serration-deformation behavior of BMGs.