Merging of relaxations and step-like increase of accompanying supercooled liquid region in metallic glasses via ultrafast nanocalorimetry

Abstract Glassy materials under external stimuli usually display multiple and complex relaxations. The relaxations and the evolution paths of glassy materials significantly affect their properties and are closely related to many key issues in glass physics, such as glass transition and thermoplastic forming. However, until now, the relaxation dynamics in the presence of external stimuli and the microscopic atomic motion of glassy materials have been unclear due to the lack of structural information. By combining Flash and conventional differential scanning calorimetry (DSC), we applied a very large range of heating rate of six orders of magnitude and investigated the relaxation dynamics of three typical metallic glasses. We discovered the merging of distinct relaxation events with increasing rate of heating. Most interestingly, the experiments revealed new behaviors with step-like increases in the supercooled liquid region and excess heat capacity during the merging of multiple relaxations. A comprehensive scheme was proposed for the evolution of the thermal relaxation spectrum, the heterogeneity of the corresponding atomic motion and the potential energy landscape with rate of heating. These experimental results shed light on the mechanism of atomic rearrangement during heating and provided a new approach to regulate the physical properties of amorphous materials by controlling their intrinsic relaxation dynamics.