Unconspicuous rejuvenation of a Pd-based metallic glass upon deep cryogenic cycling treatment

The rejuvenation behavior of a Pd-based bulk metallic glass (BMG) upon deep cryogenic cycling treatment (DCT) has been investigated in the present study. Unlike the obvious rejuvenation phenomenon of Zr-based BMGs, unconspicuous rejuvenation can be observed for the Pd-based samples. The enthalpy of relaxation, hardness and mechanical properties maintained almost unchanged after thermal cycling. The free volume in Pd-based BMG is very difficult to be induced by DCT or eliminated by relaxation annealing, which may relate with the high rigidity of cage structures and subsequently high stability of free volume. In addition, once the free volume is eliminated by annealing for Zr-based BMG, similar unconspicuous rejuvenation upon DCT occurs, which indicates the importance of free volume in the rejuvenation mechanism. These findings provide a deeper understanding between the intrinsic amorphous structures and cryogenic thermal cycling induced rejuvenation behaviors.