Thermodynamic Assessment of the Ternary B-Hf-Zr System with Refined B-Hf Description

Thermodynamic assessment of the ternary system B-Hf-Zr has been conducted by modeling the Gibbs energy of all individual phases using the CALPHAD (CALculation of PHAse Diagrams) approach. There is no ternary compound in this system. The individual solution phases, i.e., liquid, (βHf,βZr), HfB and (Hf,Zr)B2 have been modeled. The modeling covers the whole composition and temperature ranges. The Gibbs energies of HfB2 and HfB in the B-Hf system were reassessed using the two-sublattice models (B,Hf)1(B,Hf)2 and (Hf)1(B,Hf)1, respectively. A set of self-consistent thermodynamic parameters for the B-Hf-Zr system was obtained by considering the phase diagram data in the ternary system. Comprehensive comparisons between the calculated and measured phase diagram and thermodynamic data show that the experimental information was satisfactorily accounted for by the present thermodynamic description. The liquidus projection and reaction scheme of the B-Hf-Zr system are also presented.