Correlation between flow and relaxation dynamics in supercooled metallic liquid

The enthalpy relaxation time and structural α-relaxation time of bulk metallic glass (BMG) Zr41.2Ti13.8Cu10Ni22.5Be22.5 (Vit1) were measured using differential scanning calorimetry (DSC). The strain rate dependence of the flow behavior of Vit1 BMG from homogeneous flow to brittle fracture (strain rate between 10−4 and 100 s−1) was also carefully investigated via compression test at elevated temperatures above the glass transition temperature Tg. The correlation between flow and relaxation dynamics can be established based on the experimentally characterized enthalpy relaxation time and structural α-relaxation time. The specific role played by enthalpy relaxation and structural α-relaxation in the flow of supercooled metallic liquid are recognized as: enthalpy relaxation corresponds to the annihilation of the free volume and determines the presence of stress overshoot; structural α-relaxation corresponds to the diffusion of the free volume and determines the presence of brittle fracture. With the obtained results, we might draw the conclusion that glasses cannot flow, even at infinitely slow loading rate.