CAPILLARY PROPERTIES AND THERMODYNAMICS OF THE SURFACE LAYER OF Ti-Cu AND Zr-Cu MELTS

The thermodynamic theories for surface tension of solutions, Gibbs adsorption equation, surface stability condition, experimental data (composition dependences of surface tension and molar volumes of alloys), and thermodynamic activities of components by volume are used to determine the composition, integral and excess Gibbs energies of formation, and activities of components in the surface layer of Ti–Cu and Zr–Cu melts. The solutions formed in the surface layer and volume show a negative deviation from Raoult’s law. The copper adsorption curve for alloys has a slanting maximum. The composition of the surface layer differs little from that of the volume. The Gibbs energies of formation of the solution and their excess values are negative at all compositions of the surface layer. They are lower than thermodynamic values in the volume.