The viscosity of liquid alloys of polyvalent metals with Cu, Ag and Au: Theoretical treatments based on the enthalpy of mixing

The variation of the viscosity of liquid Cu-, Ag- and Au-based alloys with the composition is discussed with special emphasis on the influence of atomic interactions. The classical rigid-sphere description is extended to the case of interacting particles by adding an extra term based on the enthalpy of mixing. The agreement with the experimental viscosity isotherms is found to be reasonable. The results are compared with semi-empirical considerations based on simple physical quantities such as the diameter of the core atoms, the atomic mass, the atomic volume and the melting temperature of the constituent elements combined with the experimental enthalpy of mixing as basic input quantity. The assessment is not conclusive but the simple semi-empirical approaches appear to be well adapted to give a likewise good interpretation of the excess viscosity in liquid alloys.