Three-point bending experiments were performed on as-cast and annealed samples of Zr 52.5 Cu 17.9 Ni 14.6 Al 10 Ti 5 (Vit105) bulk metallic glasses over a wide range of temperatures varying from room temperature (293 K) to liquid nitrogen temperature (77 K). The results demonstrated that the free volume decrease due to annealing and/or cryogenic temperature can reduce the propensity for the formation of multiple shear bands and hence deteriorate plastic deformation ability. We clearly observed a sharp ductile-to-brittle transition (DBT), across which microscopic fracture feature transfers from micro-scale vein patterns to nano-scale periodic corrugations. Macroscopically, the corresponding fracture mode changes from ductile shear fracture to brittle tensile fracture. The shear transformation zone volume, taking into account free volume, temperature and strain rate, is proposed to quantitatively characterize the DBT behavior in fracture of metallic glasses.

a b s t r a c tThree-point bending experiments were performed on Zr 52.5 Cu 17.9 Ni 14.6 Al 10 Ti 5 (Vit105) bulk metallic glass (BMGs) over a wide range of ambient temperatures varying from the liquid nitrogen temperature (77 K) to about boiling water temperature (370 K). The results demonstrated that the flexural strength of the Zrbased BMG monotonously increased with decreasing of test temperature, whereas plastic deformation ability displayed a maximum at a moderate temperature (about room temperature). That is, the plastic deformation ability was deteriorated by either higher or lower temperature than room temperature through affecting shear band nucleation and propagation within materials respectively.