On the nature of the glass transition in metallic glasses after deep relaxation

We performed parallel study of calorimetric and high-frequency shear modulus behavior of Zr-based metallic glasses after deep relaxation just below the glass transition. It is shown that deep relaxation results in the appearance of a strong peak of the excess heat capacity while the shear modulus is moderately affected. A theory assuming high-frequency shear modulus to be a major physical parameter controlling glass relaxation is suggested. The energy barrier for these rearrangements is proportional to the shear modulus while its magnitude, in turn, varies due to the changes in the defect concentration (diaelastic effect). Both dependences lead to the occurrence of heat effects. The excess heat capacity calculated using experimental shear modulus data demonstrates a very good agreement with the experimental calorimetric data for all states of glasses. It is argued that the glass transition behavior after deep relaxation bears the features of a phase transition of the first kind.