Viscosity measurements of Zr55Cu30Al10Ni5 and Pd40Cu30Ni10P20 supercooled liquid alloys by using a penetration viscometer

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 degrees 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 degrees 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.