Experimental determination and thermodynamic calculation of the phase equilibria in the Co-Mn-Ta system

The phase equilibria in the Co-rich corner of the Co-Mn- Ta system were investigated by means of optical microscopy, electron probe microanalysis and X-ray diffraction. Six isothermal sections in the Co-rich corner of the Co- Mn-Ta ternary system at 1 300 °C, 1 200 °C, 1 100 °C, 1 000 °C, 900 °C, 800 °C were experimentally determined. On the basis of previous and present experimental data of the phase equilibria, the thermodynamic assessments of the Mn-Ta binary and Co-Mn-Ta ternary systems were carried out by using CALPHAD. The thermodynamic parameters of the Mn-Ta binary and the Co-Mn-Ta ternary systems have been optimized for reproducing the experimental results in each system. An agreement between the calculated results and experimental data is obtained.