Viscosity Measurements of Zr₅₅Cu₃₀Al₁₀Ni₅ and Pd₄₀Cu₃₀Ni₁₀P₂₀ Supercooled Liquid Alloys by Using a Penetration Viscometer

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Viscosity of Zr₅₅Cu₃₀Al₁₀Ni₅ and Pd₄₀Cu₃₀Ni₁₀P₂₀ 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 Zr₅₅Cu₃₀Al₁₀Ni₅ and Pd₄₀Cu₃₀Ni₁₀P₂₀ supercooled liquid alloys were about 350 and 250 kJ/mol, respectively. The viscosity was also fitted by a Vogel–Fulcher–Tammann (VFT) relationship over the entire temperature range.