Another clue to understand the yield phenomenon at the glassy state in a Zr₅₅Al₁₀Ni₅Cu₃₀ metallic glass

In the glassy temperature region from ambient to the glass transition temperature (T_g), an apparent Young's modulus (E_ap), the slope of the initial linear part on the stress-strain curve, in a Zr-based metallic glass clearly depends on both temperature and strain rate, especially above 0.87 T_g. This indicates that viscous contribution is included in this apparent elastic response. If yield strain is deduced with Young's modulus measured by the ultrasonic vibration method, which excludes the viscous contribution, temperature dependence of the yield strain can be captured well with the Argon's Shear Transformation Zone (STZ) model. On the other hand if the yield strain is deduced with E_ap, the strain was found to keep the "universal" critical value ∼ 0.020 for many metallic glasses at the ambient temperature. This may indicate another clue to understand the yield mechanism on BMG.