On the Vibration-Enhanced Thermoplastic Formability in Bulk Metallic Glasses

Abstract

Bulk metallic glasses (BMGs) hold a promising niche in the manufacture of high-performance metallic parts with intricate shapes for modern industries, wherein how to achieve superior thermoplastic formability of BMGs is most essential. In this work, vibration-enhanced thermoplastic formability was validated in 3 different types of BMGs ( i.e. Pd 40 Cu 30 Ni 10 P 20 , Zr 35 Ti 30 Be 26.75 Cu 8.25 , and La 55 Al 25 Ni 5 Cu 10 Co 5 ), suggesting that vibrational loading is a generic approach to promote the rapid forming of BMGs. Under vibrational loading, the temperature-dependent viscosity of all the 3 BMGs was found to show a more fragile behaviour at higher vibration frequency. The structural relaxation spectroscopies of the 3 BMGs after vibrational loading suggest that the vibration-enhanced formability in BMGs might originate from a unified mechanism through which vibration modulates the hierarchical atomic dynamics of BMGs. Further inspection on the fragility, structural factor, nanoindentation hardness, and relaxation enthalpy of the Pd 40 Cu 30 Ni 10 P 20 BMG indicates that the free volume content was increased at increasing vibration frequency. Aided by both experimental tests and molecular simulations, we argue that the vibration-enhanced formability in BMG is because that vibrational loading increases the free volume content while reduces the size of flow units, and most importantly, homogenises the distribution of flow units.