Revealing the connection between the slow β relaxation and sub-Tg enthalpy relaxation in metallic glasses

We report a new approach, i.e., the hyperquenching-calorimetric approach, by which the activation energy of slow β relaxation (Eβ) in metallic glasses can be determined. This method is based on the correlations among the kinetic liquid fragility index (m), the glass transition temperature (Tg), the characteristic fictive temperature (Tf,c), and the activation energy for sub-Tg enthalpy relaxation. Tf,c is the temperature at which Eβ is equal to the activation energy of the onset of the sub-Tg enthalpy relaxation of metallic glasses. The linear Tf,c/Tg ∼ m relation is attributed to the link between the contribution of the slow β relaxation to the entire relaxation process and the liquid fragility for metallic glasses. This relation is explained in terms of the potential energy landscape. The new approach reveals the inherent relation between the slow β relaxation and sub-Tg enthalpy relaxation in metallic glasses.