Viscosity measurements of Zr₅₅Cu₃₀Al₁₀Ni₅ and Zr₅₀Cu_40-xAl₁₀Pd_x (x = 0, 3 and 7 at.%) supercooled liquid alloys by using a penetration viscometer

Viscosity of Zr₅₅Cu₃₀Al₁₀Ni₅ and Zr₅₀Cu_40-xAl₁₀Pd_x (x = 0, 3 and 7 at.%) 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 K/min in the temperature range from the glass transition temperatures (T_g) up to above the crystallization temperatures. Effect of Pd addition on the viscosity of Zr-base supercooled liquid alloys has been also examined. The viscosity of these alloys decreased with increasing the heating rate and tended to saturate at the heating rate of 200 K/min and above. These viscosities can be well represented by the Arrhenius relation. The activation energy for viscous flow for Zr₅₅Cu₃₀Al₁₀Ni₅ supercooled liquid alloys was about 350 kJ/mol. In the Zr₅₀Cu_40-xAl₁₀Pd_x (x = 0, 3 and 7 at.%) alloys, the viscosities increased with increasing the Pd-content, while the activation energy for viscous flow decreased from 337 to 276 kJ/mol.