Volume and Enthalpy Relaxation in Pd_42.5Cu₃₀Ni_7.5P₂₀ Bulk Metallic Glass

Abstract

The kinetics of structural relaxation in Pd_42.5Cu₃₀Ni_7.5P₂₀ bulk metallic glass (BMG) was investigated by means of volume relaxation and enthalpy relaxation in the temperature range below T_g (≈ 573 K). The measured relaxation time was significantly longer than the α-relaxation time reported by dynamical mechanical analysis (DMA), indicating that these two relaxation processes are fundamentally different from each other. The temperature dependence of electrical resistivity suggests that the origin of the β-relaxation process that occurs between room temperature and T_g may be the compositional short range ordering. Anomalous volume expansion was observed in the initial stage of relaxation, which was attributed to annihilation of the p-type defects with very short relaxation time.