On the prediction of temperature-dependent viscosity of multicomponent liquid alloys

The simulation of casting processes demands accurate information on thermophysical properties for selected alloys to properly feed the mathematical models. One of such properties is the viscosity of pure liquid metals and alloys, which can be either found in the literature as experimental data or to be calculated by theoretical models. Nevertheless, a considerable discrepancy between experimental data and simulated results is frequently observed for some pure metals, as high as twice the experimental measured values. Several models can be found in the literature, such as those in the form of Arrhenius-type equations, which depend on the availability of experimental data with a view to permitting the apparent activation energy and the pre-exponential constant parameters to be determined. Furthermore, models based on Andrade's equation and its extensions, to deal with the apparent activation energy and the free volume concepts, are generally dependent only on thermodynamic data, that is, molar weight, molar volume, Gibbs energy of viscous flow activation, Gibbs energy and enthalpy of formation, and the molar fractions of the alloy components. In this paper, an extension of Takahira's model for pure liquid metals is proposed, which permits to deal with the viscosity of liquid multicomponent alloys. Comparisons are made among simulations provided by an Arrhenius-type equation, Kaptay's and Takahira's models for pure metals, as well as among an Arrhenius-type equation, Kaptay's model and the present approach for multicomponent alloys. The simulated results are plotted against experimental viscosity data from the literature for pure liquid metals (Al, Cu, Si and Mg) and for ternary and quaternary commercial Al-based alloys. The proposed approach for multicomponent alloys is shown to agree well with the experimental scatters and with Kaptay's model for all examined cases.