Thermodynamic analysis of the Zr–Be system using thermochemical properties based on ab initio calculations

Abstract

A thermodynamic analysis of the Zr–Be system has been carried out by combining ab initio energetic calculations with the CALPHAD approach. The energy of formation of the binary compound phases and some bcc-based ordered phases was calculated using the Full Potential Linearized Augmented Plane Wave method. The CrB-type ZrBe phase, which has been reported as a metastable phase, was found to be stable in the ground state, while the ZrBe phase with a CsCl-type B2 structure was found to be metastable. The Gibbs free energy of formation of the bcc phase was obtained by applying the cluster expansion and the cluster variation methods. To describe the B2 ordering state, the Gibbs energy of the bcc phase was represented using the two-sublattice model with the formula (Zr,Be) 0.5(Zr,Be) 0.5. Although the thermodynamic parameters for the CrB-type ZrBe phase did not satisfy both the experimental data and the ab initio calculations, the calculated phase diagram reproduced the experimental results. In addition, the glass-forming ability of this binary alloy was evaluated by incorporating the thermodynamic quantities from the phase diagram calculation into the Davies–Uhlmann kinetic approach. The evaluated glass-forming compositional range was narrower than the experimental results.