Poisson's ratio and fragility of bulk metallic glasses

Abstract

The correlation among apparent global plasticity, Poisson's ratio, and fragility in monolithic bulk metallic glass (BMG) alloys has been investigated in the present study. The shear and bulk moduli in monolithic Cu-based BMG alloys have been measured by resonant ultrasound spectroscopy (RUS) and ultrasonic technique. The Cu43Zr43Al7Ag7 BMG alloy showing a large apparent global plasticity (similar to 8%) exhibits a high Poisson's ratio when compared with that Of Cu43Zr43Al7Be7 BMG alloy. In addition, the fragility of Cu-based BMG alloys can be obtained by differential scanning calorimetry (DSC). The fragility index m of Cu43Zr43Al7Ag7 BMG alloy is slightly larger than that of Cu43Zr43Al7Be7 BMG alloy. The correlation between Poisson's ratio and fragility in BMG alloys can be presented by a simple relation of m - 17 = 14 (B-infinity/G(infinity)-1). Poisson's ratio and fragility might be regarded as an important parameter that controls global plasticity of glass-forming alloys.