Thermodynamic evaluation of the phase equilibria and glass-forming ability of the Ti−Be system

• Published in: Journal of phase equilibria and diffusion 2006-02, Vol.27 (1), p.83-91
• Main Authors: Tokunaga, Tatsuya, Ohtani, Hiroshi, Hasebe, Mitsuhiro
• Format: Article
• Language: English
• ISSN: 1547-7037; 1863-7345; 1934-7243
• DOI: 10.1361/105497106X92844

The glass-forming ability of Ti-Be alloys is of great interest. Experimental and theoretical evaluations of the glass-forming ability of this binary alloy show that the formation of a metastable TiBe phase with a CsCl-type B2 structure controls the glass-forming ability in this system. However, there is no information on the thermochemical properties of metastable TiBe for the quantitative evaluation of the glass-forming ability using Davies-Uhlmann kinetic formulations. We have carried out a thermodynamic analysis using experimental phase diagram data and the energy of formation of the stoichiometric compounds from ab initio calculations. Furthermore, the Gibbs energy of formation for the body-centered cubic (bcc) phase was evaluated over the entire composition range by applying the cluster expansion method (CEM) to the total energy of some bcc-based ordered structures obtained from ab initio calculations. For the bcc phase, the two-sublattice formalism, (Ti, Be)^sub 0.5^(Ti,Be)^sub 0.5^, was adopted to describe the A2/B2 transformation. A good agreement between the calculated values and experimental phase equilibria was obtained. Evaluation of the glass-forming ability was also attempted utilizing the thermodynamic quantities obtained from the phase diagram assessment. The calculated glass-forming ability agrees well with the experimental results.[PUBLICATION ABSTRACT]