Thermodynamic approach to free volume kinetics during isothermal relaxation in bulk Pd–Cu–Ni–P20 glasses

Isothermal relaxation behavior just under glass transition region was investigated for bulk Pd40Ni40P20 and Pd42.5Cu30Ni7.5P20 metallic glasses. The densification of the bulk sample during relaxation was examined directly by density measurement using conventional Archimedean technique. The density of as-quenched Pd40Ni40P20 increased monotonously with time. From the density data of Pd40Ni40P20 glass, the free volume relaxation was examined and the kinetics was well described by a stretched exponential function with Kohlrausch exponent less than unity. These glasses also showed a clear two-step relaxation that may be a feature peculiar to bulk metallic glasses.