Flow serration and shear-band viscosity during inhomogeneous deformation of a Zr-based bulk metallic glass

Uniaxial compressive behavior of Zr64.13Cu15.75Ni10.12Al10 bulk metallic glass at room temperature was characterized with high-sensitivity strain gauges directly attached to test samples. Displacement–time curves exhibited micron-size serrations (or bursts) after the onset of yielding, apparently associated with discrete shear band formation. Each displacement burst disclosed three-step (acceleration, steady-state, and deceleration) process in shear band propagation. The viscosity of a propagating shear band was found to be relatively low and, actually, in a similar range usually measured in the supercooled liquid region. A detailed analysis of the experimental results using a self-consistent Vogel–Fulcher–Tamann (VFT) equation based on free volume model suggested that shear band propagation was mainly resulted from free volume accumulation.