Structural rejuvenation and toughening of bulk metallic glass via ultrasound excitation technique

Bulk metallic glasses (BMGs) represent a class of solid materials which have randomly packed atomic structure in long range but exhibit unique properties. Nowadays, the macroscopic brittleness at ambient temperature is the fundamental and intriguing issue to impede the engineering application of BMGs. In this article, we report a breakthrough in solving the strength-ductility tradeoff dilemma of BMGs by introducing strong forced vibration of atoms named ultrasonic vibration (USV) technique. We find that not only the ambient temperature compressive plasticity is remarkably increased but also yield strength is augmented by kHZ level USV treatment. The toughening of BMGs has also been evidenced by the pronounced increase in the first pop-in event, which represents by the critical stress to stimulate the initial yield with the formation of shear band. It has also been confirmed that the free volume in USV treated BMGs is strikingly increased. Therefore, the intrinsic mechanism of USV induced toughening can be interpreted in the frame of structural heterogeneities and energy landscape theory, i.e., the USV induced structural rejuvenation by increasing the loosely packed soft regions and decreasing the closely packed hard regions. The basins that possess larger potential energies are overwhelmingly increased after USV treatment. Our findings provide a new approach for surmounting strength-ductility trade-off dilemma of single atom glassy matter such as BMGs.