Quantitative assessment of physical aging on dynamical heterogeneity of amorphous alloys: Insight from stress relaxation

Probing the dynamical and structural heterogeneity is a critical issue for understanding the mechanical and physical properties of amorphous alloys. Here, the stress relaxation of a (La_0.6Ce_0.4)₆₅Al₁₀Co₂₅ amorphous alloy is investigated to probe the evolution of dynamical and structural heterogeneity due to aging. The characteristics of amorphous alloys are time-dependent during stress relaxation due to the metastability; thus, the aging effect should be considered by modifying the classical Kohlrausch-Williams-Watts (KWW) function. We find that the fixed-parameter KWW function during prolonged stress relaxation is not valid due to aging. Furthermore, the parameters of the modified KWW function indicate that physical aging leads to an increase in the characteristic time τ and decrease in the stretched exponent β KWW . The latter widens the instantaneous stress relaxation curve toward long-time end. The results demonstrated that the modified KWW function and the corresponding parameters conform to the conventional understanding of amorphous alloys.