Rejuvenation Behavior and New Classification of β-relaxation Region in Pd-based Metallic Glass

Abstract

We have focused on a rejuvenation behavior of recovery annealed Pd42.5Cu30Ni7.5P20 metallic glass. Specific heat measurement results revealed that only 33%, which is lower than that (44%) of a Zr50Cu40Al10 metallic glass, was recovered by annealing. This result indicates that the recovery of a Pd42.5Cu30Ni7.5P20 metallic glass is more difficult than the Zr-based alloy. The hardness measurement results obtained from the indentation test also supported this finding. The time dependence of the normalized storage modulus E'/Eu at 0.8Tg of both metallic glasses were successfully demonstrated by the KWW (Kohlrausch-Williams-Watts) equation, which means that the relaxation/rejuvenation behavior of each sample was well described by the free volume change. It also suggested that the distribution of relaxation modes of the Pd42.5Cu30Ni7.5P20 metallic glass is much narrower in a β-relaxation region. The normalized loss modulus E"/Eu implied that two areas, one is in correlation to the free volume change and the other is not, are embedded in the intrinsic β-relaxation region and the lower rejuvenation ability in the Pd42.5Cu30Ni7.5P20 metallic glass may originate from a low volume fraction of the former area. The present study will provide the universal information for the research subject on the thermal rejuvenation in metallic glasses.

Synthesis and mechanical properties of highly structure-controlled Zr-based metallic glasses by thermal rejuvenation technique

“…This suggests the relaxation state could be controlled solely through a conventional thermal process. We confirmed that rejuvenation can occur in fully relaxed Zr-Al-Ni-Cu and Pd-Cu-Ni-P disc metallic glasses, accompanied by an increase in relaxation enthalpy, a decrease in density, and mechanical softening by annealing at temperatures higher than T g followed by cooling at a rate of a few K s -1 [16,40]. These results demonstrate the occurrence of rejuvenation caused by the simple process of annealing and cooling.…”