Rate Dependence of Serrated Flow and Its Effect on Shear Stability of Bulk Metallic Glasses

The rate dependence of serrated flow and its effects on the stability of shear banding were systematically investigated in a prototypic bulk metallic glass. It was found that with the increase of external strain rate, the serrated flow is gradually suppressed and could completely disappear at a critical strain rate. The serration size, characterized by the mean stress drop amplitude, decreases inversely with the strain rate, while the waiting time for serration decreases with the strain rate in a power-law manner. The rate dependence of the serrated flow has important effects on the dynamics and stability of shear banding process, and leads to an optimal plasticity achieved around the critical strain rate for the disappearance of serrated flow. These results are discussed and interpreted in terms of the microscopic deformation theory and the stick-slip dynamics of shear banding for bulk metallic glasses.