The rheological behavior and constitutive model of Zr35Ti30Be27·5Cu7.5 metallic glass under high strain rate tensile conditions within the supercooled liquid region

Abstract

Tensile rheological behavior of the Zr35Ti30Be27·5Cu7.5 metallic glass under conditions of high strain rates (strain rates ranging from 0.05 s−1 to 0.5 s−1) within the supercooled liquid region was studied. The stress-strain curve reveals that this metallic glass demonstrates non-Newtonian flow characteristics under these circumstances. The peak stress associated with stress overshoot increases as temperature decreases and strain rate increases. However, the steady-state flow stress displays an anomalous decrease due to rapid necking at high strain rates. Subsequently, the thermal processing map of the Zr35Ti30Be27·5Cu7.5 metallic glass was established and analyzed. It reveals that the alloy has relatively excellent thermoplastic forming ability at temperature between 630 K and 655 K and strain rates between 0.05 s−1-0.2 s−1. We found that under strain rates ε˙≥10−2s−1, the strain rate is the primary factor influencing normalized viscosity. Therefore, we developed a simplified Maxwell-Pulse constitutive model applicable to metallic glass in the supercooled liquid region under high strain rate conditions, by simplifying the constitutive equation for steady-state flow stress using a simplified formula for normalized viscosity calculation. The predictions of this simplified modified model align well with experimental values. By comparing the simplified and unsimplified Maxwell-Pulse constitutive models, the overall fitting accuracy of the simplified model was improved by 3–5%, with the highest improvement of 67% in the steady-state flow stress stage. These results indicate that the modified model accurately reflects the stress-strain relationship for the Zr35Ti30Be27·5Cu7.5 metallic glass under high temperature and high strain rate tensile conditions.