Experimental investigation and thermodynamic calculation of the phase equilibria in the Co–Nb–Ta ternary system

The isothermal sections of the Co–Nb–Ta ternary system at 900 °C, 1000 °C, 1100 °C, 1200 °C, 1300 °C have been experimentally determined by electron probe microanalysis (EPMA) and X-ray diffraction (XRD) techniques on the equilibrated alloys. On the basis of the experimental data investigated in the present work, the phase equilibria in the Co–Nb–Ta system has been thermodynamically assessed by using CALPHAD (CALculation of PHAse Diagrams) method, and a consistent set of the thermodynamic parameters leading to reasonable agreement between the calculated results and experimental data was obtained.

Research highlights▶ This work is to systemically carry out the experimental investigation of the phase equilibria in the Co–Nb–Ta ternary system. ▶ On the basis of the experimental data obtained from the present work, the phase equilibria in the Co–Nb–Ta system were thermodynamically assessed by using CALPHAD method. ▶ A consistent set of the thermodynamic parameters leading to reasonable agreement between the calculated results and experimental data was obtained.