Evolution of the distribution of flow units of a metallic glass under cyclic loading

Dynamic mechanical relaxation processes (i.e., β relaxation and α relaxation) are closely connected with the mechanical and physical properties of metallic glasses. In the current work, the β relaxation of La₆₀Ni₁₅Al₂₅ metallic glass was studied in sequential heating and cooling experiments by dynamic mechanical analysis. The values of the loss modulus peak were found to reach a relatively stable state during the progress of the heating-cooling cycles. The evolution of the flow unit distribution during thermal cycling was revealed by stress relaxation tests. The experimental results of stress relaxation were well described by a generalized Maxwell model, allowing the analysis of the underlying relaxation time and activation energy distributions. We also show here a suppressed relaxation behavior observed under repeated loading cycles, which is attributed to the annihilation of flow units and the modification of the relaxation time spectrum obtained in the framework of the generalized Maxwell model.