Reversible structural relaxation in metallic glasses

Abstract

Reversible structural relaxation effects in metallic glasses have been studied by the enthalpy relaxation technique using a differential scanning calorimeter. It is shown that the experimentally determined magnitude of the reversible relaxation effect is critically dependent on crystallization and/or irreversible relaxation processes. Results are given for a variety of metallic glasses including metal-metalloid, and a number of binary and ternary transition metal glasses. Within each series of alloy glasses, the magnitude of the reversible relaxation scales with the annealing temperature if normalized to the glass transition temperature. The increase in the reversible effect shows a monotonic increase with the concentration of the more mobile (diffusive) atomic species. This indicates that chemical short-range order plays no role in reversibility and the data have been qualitatively modelled by assuming simply that reversible relaxation is caused by the thermal repopulation of excited structural states.