Kinetics of structural relaxation in glasses: A hierarchical model of relaxation centers

A definition is proposed for the characteristic time of structural relaxation τ_{str. rel} in metallic glasses—the universal parameter describing the kinetics of various processes associated with the structural relaxation. The behavior of τ_{str. rel} in model situations of isothermal annealing of a glass and its heating at a constant rate is considered. In the former case, the time τ_{str. rel} is equal to the age of the sample. In the latter case, after a time, τ_{str. rel} reaches a steady-state value. This is in agreement with the τ_{str. rel} values determined from the creep rate. The kinetics of structural relaxation is analyzed with due regard for the hierarchical structure of the phase space in glasses. The kinetic equation taking into account this feature is proposed, and the results of its numerical solution are given.