Cryogenic effects on the mechanical behavior of bulk metallic glasses

Abstract

Abstract. Bulk metallic glasses (BMGs), unlike crystalline alloys, exhibit significantly enhanced plastic deformation when tested at cryogenic temperatures. This enhanced plasticity is primarily characterized by the slowed propagation of shear bands and the formation of multiple shear bands, which play a crucial role in the material's behavior at low temperatures. Due to their amorphous nature, BMGs are prone to catastrophic fractures once shear band nucleation and propagation occur, a behavior distinct from that of crystalline materials. However, the underlying mechanisms of BMG failure and the effect of strain rate remain controversial. This study investigates the mechanical behavior of a Zr-based BMG under cryogenic conditions. Compression tests were conducted at room temperature and -180°C, using liquid nitrogen, across a range of strain rates. The results show that, at cryogenic temperatures, ductility increases, though it remains relatively low, leaving uncertain its impact on machinability. Notably, larger stress drops were observed at ambient temperature, likely linked to shear band formation. Additionally, the study identified two distinct fracture modes during dynamic tests, warranting further investigation. This research provides valuable insights into the behavior of BMGs under cryogenic conditions and their machinability.