Constitutive model for inhomogeneous flow in bulk metallic glasses

Abstract

This study presents results on the mechanical properties of Zr-based bulk metallic glasses over a wide range of temperatures (77–673 K) and strain rates (3.3 × 10 −5 − 0.2 s −1), and provides novel information on the kinetics of inhomogeneous deformation in metallic glasses. The disappearance of serrated flow, i.e. temporal homogenization, below a critical temperature and above a critical strain rate corresponds to a transition of the asymptotic strain rate sensitivity (SRS) from negative to positive values. Based on thermally activated shear processes a temperature and strain rate dependent deformation model is presented that includes a time-varying state variable which represents the local degree of relaxation in the shear band after a shear event has taken place. The model makes possible a theoretical description of the observed SRS and the spatio-temporal evolution of plastic deformation in metallic glasses.