Density and Surface Tension of Liquid Ternary Ni–Cu–Fe Alloys

The density and surface tension of liquid Ni–Cu–Fe alloys have been measured over a wide temperature range, including the undercooled regime. A non-contact technique was used, consisting of an electromagnetic levitator equipped with facilities for optical densitometry and oscillating drop tensiometry. At temperatures above and below the liquidus point, the density and surface tension are linear functions of temperature. The concentration dependence of the density is significantly influenced by a third-order (ternary) parameter in the excess volume. The surface tensions are rather insensitive to substitution of the two transition metals Ni, Fe against each other and depend only on the copper concentration. By numerically solving the Butler equation, the surface tension of the ternary system can be derived from the thermodynamic potentials EG of the binary phases (Ni–Cu, Fe–Cu, Ni–Fe) alone.