Thermodynamic modeling of the Zr–H–Nb system on the Zr-rich side and application

A thermodynamic modeling of the Zr–H–Nb system on the Zr-rich side (wt.%Nb ⩽ 2.5) was established using CALPHAD (CALculation of PHAse Diagrams) method. The calculated pressure-composition isotherms and the composition limits in the two-phase (bcc + fcc) region agree well with the experimental data. Meanwhile, some thermodynamic data of Zr–H–Nb system (wt.%Nb = 1, PH2PH2=101.325 kPa) was calculated, such as equilibrium hydrogen concentration, phase composition and phase transition temperature, which was applied to guide the preparation of the crack-free zirconium hydride. The hydriding of Zr–1 wt.%Nb alloys was carried out and the crack-free zirconium hydrides with hydrogen concentration of 1.6H/Zr (at.) and 1.8H/Zr were prepared respectively based on the calculated results.