Long-term elasto-static compressive loading drives rejuvenation of a metallic glass

Abstract

The current work focuses on the impact of mechanical protocol which can lead to either rejuvenation or relaxation of metallic glasses (MGs) through elasto-static compressive loading (ECL) treatment. Here we demonstrate that, even after imposing a long-term ECL process, the Zr52.5Cu17.9Ni14.6Al10Ti5 MG subjected to an elasto-static stress of 85% of the yield stress at room temperature shows varying degrees of rejuvenation without any relaxation. The MG undergoes an increasing trend in structural rejuvenation with an increased stored energy and a more disordered structure. Nanoindentation results reveal that the variation of mechanical responses emerges from the complementary effects of the thermal activation process and the structural heterogeneity of glassy phase. The spital heterogeneities can effectively reduce the activation barriers of the shear transformation zones (STZs) and widen their distributions, which will perturb the shear-banding processes from single motion to collective movements, leading to shear band multiplication/branching and an increase in the elastic energy density cut-off. As a result, the plasticity is significantly enhanced and the yield strength is decreased. These findings shed light on that ECL process is an effective way to enhance the structural heterogeneity and the level of rejuvenation of a monolithic MG, which may allow the design of MGs with desirable mechanical properties.