Surface segregation and surface tension in Al–Sn–Zn liquid alloys

Abstract

A new expression for the surface tension ( σ ) of ternary liquid alloys has been developed in terms of surface composition and similarity coefficients ( ξ ij ) which takes into account the correlation between the component atoms of the system. The expression involves the same ordering energies for the concerned binaries as used for its bulk and surface calculations and bulk calculation of the ternary system. Our theoretical investigation successfully reproduced the experimental findings for all concerned binaries of the Al–Sn–Zn system. The surface is quite enriched with Sn atoms in the Sn–Zn and Al–Sn systems while the Al–Zn system exhibits segregation of Zn atoms at the surface. σ decreases with Sn concentration in both Sn–Zn and Al–Sn systems. In the Al–Zn system it decreases with the increase of Zn content. In the Al–Sn–Zn system a slight decrease in σ is observed. σ -is almost the same up to 20% aluminium in the three cross-sections of Sn and Zn, i.e. 1:1, 1:2 and 2:1. σ increases beyond this concentration in all cross-sections. The surface is quite enriched with Sn atoms—the maximum being at the 2:1 and the minimum at the 1:2 cross-section.