Temperature and Time Dependences of the Viscosity of InBi–Pb Melts

Abstract

Temperature and time dependences of the viscosity of InBi_100 – хPb_х melts (where х = 0, 19, 40, 60, 80, 100 at %) have been studied by the method of damped torsional oscillations. Intermediate compositions of this system have been studied for the first time. It has been demonstrated that the viscosity and the oscillation period curves for InBi–Pb melts containing up to 40 at % Pb measured in the heating and cooling modes are coincident and monotonic. In the InBi₄₀Pb₆₀ melt, the hysteresis of the viscosity and oscillation period of the suspension system with the melt is observed only in the first heating–cooling cycle, and in InBi₂₀Pb₈₀, after the first heating–cooling cycle, the viscosity hysteresis changes sign from negative to positive. From the results of measurements of the time dependences of the viscosity of the InBi₄₀Pb₆₀ melt at a constant temperature, the relaxation time is determined, which decreases exponentially with increasing temperature. The activation energy of the melt homogenization process was found to be E_a = 83 kJ/mol. The relaxation time and activation energy of the homogenization process determined in this work significantly exceed the values obtained in the literature for other systems. The long relaxation time near the liquidus suggests that this nonequilibrium state in the InBi₄₀Pb₆₀ melt is metastable.