Decoupling between enthalpy and mechanical properties in rejuvenated metallic glass

The mechanical properties of amorphous materials are closely related to their energy states (enthalpy). Usually, a higher energy state corresponds to larger plasticity and lower hardness. Here, we explore the correlation between the enthalpy and hardness of rejuvenated Au-based metallic glasses (MGs). We found that the rejuvenated MG with a high-energy state presents a hardness variation trend different from before, i.e. the hardness increases instead of keeping on decreasing with increasing enthalpy when the enthalpy is higher than an intermedia value. It is revealed that both the reactivations of β- and α-relaxation are beneficial to increasing the enthalpy but show opposite effect on the hardness. This study shows that this decoupling may be originated from the beginning of the reactivation of α-relaxation. Our work provides new insights into designing MGs with excellent mechanical properties by rejuvenating relaxed MGs via the furthest reactivation of β-relaxation and avoiding reactivation of α-relaxation.