Viscosity measurements of Zr ₅₅Cu ₃₀Al ₁₀Ni ₅ and Pd ₄₀Cu ₃₀Ni ₁₀Pi ₂₀ supercooled liquid alloys by using a penetration viscometer

Viscosity of Zr ₅₅Cu ₃₀Al ₁₀Ni ₅ and Pd ₄₀Cu ₃₀Ni ₁₀Pa ₂₀ supercooled liquid alloys having bulk metallic glass forming ability has been measured by using a penetration viscometer with a cylindrical probe under high speed heating conditions at heating rates between 20 and 400°C/ min in the temperature range from the glass transition temperatures (T _g) up to above the crystallization temperatures. The viscosity of these alloys decreased with increasing the heating rate and tended to saturate at the heating rate of 200°C/min and above. Their viscosity could be well represented by the Arrhenius relation. The activation energies for viscous flow for Zr ₅₅Cu ₃₀Al ₁₀Ni ₅ and Pd ₄₀Cu ₃₀Ni ₁₀P ₂₀ supercooled liquid alloys were about 350 and 250kJ/mol, respectively. The viscosity was also fitted by a Vogel-Fulcher-Tammann (VFT) relationship over the entire temperature range.