Abstract:The mechanical properties of the Zr_52.5Cu_17.9Ni_14.6Al₁₀Ti₅ alloy were presented, with an emphasis on the strain rate effect and presence of crystalline inclusions on the deformation and fracture mechanisms. X-ray diffraction studies indicated fully amorphous alloy structures with lower oxygen contents and partial crystalline structures at higher oxygen levels; however, completely different compressive deformation behaviour was observed. Uniaxial compression tests of the fully amorphous alloy showed elastic deformation, followed by yielding, distinct plastic deformation and serration flow behaviour. An increase in strain rate from 1×10^-4 to 1×10^-2 s^-1 did not affect the yield strength; however, it decreased the compressive fracture strength and reduced the plastic strain. Scanning electron microscopy (SEM) observations with energy dispersive spectroscopy (EDS) analysis showed that the intermetallic CuZr₂ phase was present even in the low oxygen content alloy, leading to lower fracture strength and ductility loss. For the high oxygen level samples, the presence of the dendritic Zr₅₁Cu₂₈Al₂₁ phase was confirmed, leading to fracture strength impairment. The difference between ductile and brittle samples has been reflected on the fracture surfaces. The higher the plastic strain was, the higher the density of shear bands forming during deformation manifested by a serration flow behaviour on stress-strain curves.

Key words: bulk metallic glasses; compression test; shear band; X-ray diffraction