Identifying the high entropy effect on plastic dynamics in bulk metallic glasses: A nanoindentation study at room and elevated temperatures

In this study, the spatiotemporal dynamic analyses of intermittent plastic flow in the nanoindentation of different Bulk metallic glasses (BMGs), at various temperatures, were carefully performed to provide insight into the amorphous structural-property relationship. Based on the displacement-time series and largest Lyapunov exponent during serrated flow, two distinct types of dynamic behaviors were identified at room temperature, i.e., the serrated flow dynamics transforms form a self-organized critical state in traditional BMGs to a more chaotic state in high entropy BMGs (HE-BMGs). This may originate from their local structural difference that the solvent-solute architecture in conventional BMGs is broken in HE-BMGs. Furthermore, sluggish diffusion in HE-BMG can effectively retard relaxation kinetics, which leads to the deviation of HE-BMGs from the conventional BMGs in terms of the relationship between the chaotic behavior and temperature. Indeed, the insignificant change in dynamic complexity of HE-BMG conforms to its increased structural stability at elevated temperatures, which was soundly elucidated from both topological and kinetic factors. This study is of significance in understanding the configuration complexity and structure stability in HE-BMGs and helpful for designing BMGs with promising properties against external mechanical and thermal agitations.