Stress relaxation in high-entropy Pd₂₀Pt₂₀Cu₂₀Ni₂₀P₂₀ metallic glass: Experiments, modeling and theory

The viscoelastic properties of Pd₂₀Pt₂₀Cu₂₀Ni₂₀P₂₀ high-entropy metallic glass were probed by dynamic mechanical spectroscopy and stress relaxation. The experimental evolution of stress can be characterized by the empirical Kohlrausch-Williams-Watts function during the tensile stress relaxation measurement. We develop a linear relaxation model able to describe the whole process of stress relaxation in a wide range of temperatures. The linear relaxation model takes into account the microstructural heterogeneity of the glass, and thus its dynamical heterogeneity, so that the thermal effect and stress-driven process are physically decoupled. The activation energy spectra at various temperatures reveal the changes of the deformation units during stress relaxation, which is the result of the interplay between stress and temperature. This study decomposes the widespread hierarchical dynamics due to structural heterogeneity which accommodates the viscoelastic deformation of the high-entropy metallic glasses.