Anomalous temperature dependence of sound velocity in Zr₅₀ Cu₄₀Al₁₀ with different excess free volume

Temperature dependence of the mechanical resonance frequency f_m of ultrasonic wave in as-quenched and annealed Zr₅₀Al₁₀Cu₄₀ metallic glasses was measured from room temperature to liquid nitrogen temperature. The mechanical resonance of longitudinal wave for the as-quenched sample disappeared in lower temperature below 200 K. The resonance was restored at about 240K with increasing temperature. A hysteresis was observed in temperature dependence of f_m. The qualitatively similar behaviors were observed also for transverse wave. The phenomena for the annealed samples are different from ones for the as-quenched one. The excess free volume may cause anomalous temperature dependence of f_m.