Effect of Ta on glass formation, thermal stability and mechanical properties of a Zr 52.25Cu 28.5Ni 4.75Al 9.5Ta 5 bulk metallic glass

Abstract

The effect of Ta on glass-forming ability, crystallization behavior and mechanical properties of Zr 52.25Cu 28.5Ni 4.75Al 9.5Ta 5 bulk metallic glass (BMG) is investigated. The solubility of Ta in the Zr-base BMG alloy depends on the arc melting conditions. 3.2 at.% Ta dissolve in the alloy inducing an increase of about 20 K in both glass transition temperature and crystallization temperature of the BMG. However, Ta does not significantly change the extension of the supercooled liquid region. The remaining Ta particles in the master alloy may induce a composition-segregation layer around the particles upon subsequent casting. This further induces the crystallization of Zr 2Cu that deteriorates the ductility of the samples. The compressive strength and ductility of the as-cast 3 mm diameter Zr 52.25Cu 28.5Ni 4.75Al 9.5Ta 5 samples are improved in comparison with the Zr 55Cu 30Ni 5Al 10 BMG alloy. The fracture plane of the present alloy has an angle of 31–33° with respect to the stress axis, which remarkably deviates from the maximum shear stress plane. The improvement of the mechanical properties and the peculiar fracture feature for the Zr 52.25Cu 28.5Ni 4.75Al 9.5Ta 5 BMG alloy can be attributed to the effect of dispersed Ta particles.