Thermal rejuvenation of an aged Au-based metallic glass by fast scanning calorimetry

Abstract

A metallic glass (MG) annealed above its glass-transition temperature Tg, and cooled, may show an enthalpy increase ΔH, and other property changes. The extent of this thermal rejuvenation depends on the state of the MG (represented by effective cooling rate Φi) and the post-anneal cooling rate Φc. Previous studies examined effects of (Φc/Φi) up to 102. With a Au-based MG aged for up to 10 years at room temperature, and using fast calorimetry to anneal and then cool at up to 5000 K s−1, we extend (Φc/Φi) to 107. The rejuvenation is limited by anneal temperature or by Φc, when, for all MGs, ΔH/Tg shows a universal approximate scaling with log(Φc/Φi). We detect decoupling of vitrification from α relaxation, and highlight limitations in the use of fictive temperature to characterize glassy states. Rejuvenation of the Au-based MG decreases its elastic modulus and hardness, extending trends reported for other MGs.