Tailoring rejuvenation behavior of Zr-based metallic glass upon deep cryogenic cycling treatment

The rejuvenation behavior of a Zr55Cu30Ni5Al10 (at.%) metallic glass upon deep cryogenic cycling treatment was investigated. The sample was rejuvenated to a larger extent with increasing cyclic number, resulting in a higher enthalpy of relaxation and a lower density. The rejuvenation seems to be saturated after 200 cycles, which may originate from the limited content of free volume in the amorphous structure. The sample subjected to a higher cyclic number showed a lower hardness and better plasticity due to a larger shear transformation zone (STZ) volume. In this case, a lower shear plane formation energy facilitates the generation of multiple shear bands. Furthermore, it is found that the content of free volume has linear relationship with the plastic strain and the STZ volume. The results from molecular dynamics simulation also demonstrates that the atomic volume saturates with a higher degree of rejuvenation at a higher cooling rate of the simulated sample.