Thermodynamic assessment of the Au-Zn binary system

The phase diagram of the Au-Zn binary system may play an important role in developing new Au-base solders. In this paper, the Au-Zn binary system has been thermodynamically assessed with the CALPHAD method. Excess Gibbs energies of solution phases, liquid, fcc, hep, and c were formulated with the Redlich-Kister expression, while the intermediate phases were modeled with (Au,Zn)(0.5):(Au,Zn)(0.5) for beta', (Au)(0.6):(Au,Zn)(0.2):(Zn)(0.2) for alpha(1), (Au)(0.64286):(Au,Zn)(0.25):(Zn)(0.10714) for alpha(3), (Au,Zn)(0.15385):(Au)(0.15385): (Au,Zn)(0.23077):(Zn)(0.46153) for gamma(3), and (Au)(0.12):(Au,Zn)(0.16):(Zn)(0.72) for gamma(3), and the other phases including alpha(2), epsilon, Au5Zn3, gamma(2) and delta were treated as stoichiometric compounds according to their composition ranges. Based on the reported thermodynamic properties and phase boundary data, the thermodynamic parameters of these phases were optimized, which give a reasonable agreement between thermodynamic properties and phase diagram. (C) 2003 Elsevier Ltd. All rights reserved.