Effects of chemical composition and test conditions on the dynamic tensile response of Zr-based metallic glasses

Abstract

The effects of impact velocity and temperature on the dynamic mechanical behavior of two bulk metallic (BMG) alloys with slightly different elemental compositions (Zr 55 Cu 30 Ni 5 Al 30 and Zr 46 Cu 38 Ag 8 Al 38 ) have been investigated. Bullet-shaped samples were accelerated by a gas gun to speeds in the 400~600m/s range and tested at both room temperature and 250°C. The samples impacted steel extrusion dies which subjected the bullets to high strains at relatively high strain-rates. The extruded fragments were subsequently soft recovered by using low density foams and examined by means of optical/scanning electron microscopy and differential scanning calorimetry. It was found that shear banding was the dictating mechanism responsible for the fracture of all BMGs. At room temperature, the Zr 55 Cu 30 Ni 5 Al 30 alloy exhibited a higher resistance to fragmentation than the Zr 46 Cu 38 Ag 8 Al 38 alloy. At 250 °C, significant melting was observed in the recovered fragments of both alloys, which indicates that the BMG glassy structure undergoes a melting process and deformation likely occurs homogeneously.