Probing the Dynamic Heterogeneity of an Amorphous Alloy from the Perspective of Stress Relaxation

Abstract

Stress relaxation experiments on a Zr₅₀Cu₃₄Ag₈Al₈ amorphous alloy reveal that its dynamic heterogeneity is captured by a Kohlrausch–Williams–Watts stretched exponential function, demonstrating a non-Gaussian, asymmetric relaxation spectrum. The analysis based on the generalized Maxwell model revealed that the relaxation process is accelerated at high temperatures, indicating that increasing temperature makes more deformation units and promotes the formation of “liquid-like” zones. \({\beta }_{\text{KWW}}\) exhibits a non-monotonous trend with temperature due to the combined effects of temperature and structural relaxation. Physical aging improves structural stability by shifting the activation energy distribution toward higher values for increasing aging times. This results in a system energetic state closer to equilibrium, lowering the overall energy level and suppressing the relaxation process. Notably, it is found that the dynamic heterogeneity does not decrease but instead increases with aging. These findings provide significant insights into the structural origins of the viscoelastic behavior of amorphous alloys.