Elasticity and anelasticity of metallic glass near the glass transition temperature

Resonance ultrasound spectroscopy with piezo-electric transducers were used to probe the temperature dependence of elastic and anelastic properties and the accelerated crystallization by mechanical vibrations of a Pd-based bulk metallic glass with the glass transition temperature of approximately 300 °C. Similarly to conventional crystalline metals, the elastic stiffness constants monotonically decrease upon heating. However, the ratio of changes in the shear and bulk moduli (ΔG/ΔB) from 20 to 290 °C is 7.5, which is much larger than that of conventional crystalline metals of about 2. The internal friction increases as the temperature increases, but is nearly constant in the supercooled liquid state. After annealing for 180 min at 320 °C, the elastic constants increase about 5–10%; indicating that partial crystallization occurs during the heat treatment. In addition, this work clearly implies that applying pure ultrasound vibrations in the supercooled liquid state accelerates the crystallization of bulk metallic glass.