Free energy spectra for inelastic deformation of five metallic glass alloys

The activation free energy spectra for isoconfigurational flow of Al₂₀Cu₂₅Zr₅₅,Cu₄₀Zr₆₀, Cu₅₆Zr₄₄, Cu₆₀Zr₄₀, and Pd₈₀Si₂₀ have been measured in experiments of recovery creep at stepwise increasing temperatures performed on structurally stabilized specimens that have been previously mechanically polarized by creep over a long period of time at T_g ? 150 K, followed by freezing under stress to 220 K and removal of stress. The spectra are continuous functions rising sharply from very low values at about 20 K cal mol^?1 to peak cut-off values at the activation energy for steady state isostructural viscous flow at about 45–55 K cal mol^?1. The shapes of these spectra resemble mirror images of the cavity size distributions computed for hard sphere models of glasses and the known free area distributions in glassy rafts of soap bubbles, and suggest the existence of a direct mapping between them. A small low temperature peak at about 22–25 K cal mol^?1 has been observed in Cu₅₆Zr₄₄ and Cu₆₀Zr₄₀.