Strain Rate Sensitivity in Zr-based Metallic Glass: Experiments and Molecular Dynamics Study

This study presents results on the strain rate sensitivity (SRS) of Zr-based metallic glass over a wide range of specimen size (macro and micro) and strain rates (quasi-static and dynamic), and provides information on the correlation among shear band initiate, stress concentration and strain rate in metallic glass. Shear bands readily initiate from stress concentration sites, and metallic glasses are more sensitive to stress concentration at high strain rate. The inevitable stress concentration in bulk metallic glass could result in negative SRS. While its SRS could be enhanced by reducing the stress concentration extent. Even positive SRS could be obtained in micro-pillar metallic glass with little stress concentration. Molecular dynamics simulations show that metallic glass without defects (i.e. stress concentration) exhibits positive SRS, because the atomic mobility is not sufficient for the shear transformation zone operation to initiate a shear band at higher strain rate.