Thermodynamic assessment of Au-Zr system

Abstract

Au-Zr binary system was reassessed by using the calculation phase diagram (CALPHAD) technique based on experimental thermodynamic data and newly reported phase diagrams. The excess Gibbs energies of the three terminal solutions and the liquid phases were formulated with Redlich-Kister polynomial. All the intermetallic phases were treated as stoichiometric compounds with the exception of ZrAu which is modeled by a two-sublattice model, (Au,Zr) : (Au,Zr). The results show that there exist seven intermetallics: Zr₃Au, Zr₂Au, Zr₅Au₄, Zr₇Au₁₀, ZrAu₂, ZrAu₃, and ZrAu₄ in the system. The eutectoid reaction: β(Zr) → α(Zr)+Zr₃Au takes place at 1048 K and the maximal solubility of Au in α-Zr is 4.7% (mole fraction). The maximal solubility of Zr in Au is 6.0% (mole fraction) at 1347 K. The homogeneity range of ZrAu phase is about 44.5%–52.9% (mole fraction) of Au. The present assessment fits experimental data very well.

Keywords

Au-Zr system / CALPHAD / two-sublattice model