Differential structural evolution-driven rejuvenation mechanisms in Cu-Zr-based metallic glasses under cyclic loading

Abstract

In this study, molecular dynamics simulations were employed to investigate the effects of Al addition on the rejuvenation behavior and atomic-scale mechanisms of Cu-Zr-based metallic glasses (MGs) under cyclic loading. The research focused on the Cu₄₆Zr₅₄ binary and Cu₄₆Zr₄₆Al₈ ternary metallic glass (MG) systems. It was found that cyclic loading significantly increased the potential energy and free volume of both MGs, leading to structural rejuvenation. The addition of Al significantly accelerated the growth of potential energy and the degree of rejuvenation of the Cu₄₆Zr₄₆Al₈ MG at the initial stage of cyclic loading. In contrast, the Cu₄₆Zr₅₄ MG exhibited a higher upper limit of potential energy growth in the later stage (the saturated energy state has increased by 0.37 %). Based on the analysis of short-range order (SRO) and medium-range order (MRO), it was found that the rejuvenation mechanism of the Cu₄₆Zr₅₄ MG was characterized by an increase in icosahedral order (saturated ΔF_p= +0.36 %), which originated from the energy storage achieved through the reconstruction of icosahedral clusters dominated by Cu atoms. On the other hand, the rejuvenation mechanism of the Cu₄₆Zr₄₆Al₈ MG was characterized by a decrease in icosahedral order (saturated ΔF_p= -1.75 %), which was attributed to the regulation of the local bonding environment and structural heterogeneity by Al atoms. These findings challenge the traditional view of rejuvenation mechanisms that rely solely on structural disordering and free volume, and reveal a new pathway for energy storage in MGs through highly ordered structures.