Thermodynamic assessment of the In–Ir system in the In rich part

Optimization by the CALPHAD method of the thermodynamic parameters of the In–Ir system has been carried out using the experimental phase diagram data and thermodynamic properties. The numerous experimental data of the liquid phase determined in the 0 < x(Ir) < 0.35 composition range by two authors are coherent and associated with the scarce enthalpies of formation of the two intermetallic compounds allowed to optimize a set of coherent thermodynamic parameters in order to calculate the phase diagram in the In rich part. In the 0.40 < x(Ir) ≤ 1 composition range, the phase diagram seems more complex than the schematic part extrapolated at high temperature and the agreement between the calculated diagram and this extrapolated experimental part is not satisfactory. Further experimental investigations are needed to improve the calculation in this composition range, but which are difficult because hampered by different phenomena.

► The optimised In rich part of the In–Ir system in the present work will serve as a binary constituent for some ternary systems we are studying.
► A coherent set of thermodynamic parameters was optimized based on the CALPHAD approach, which led to the calculation of a phase diagram which is in good agreement with the experimental part determined up to about x(Ir) = 0.35.
► The calculated integral and partial enthalpies of mixing of the liquid phase are also in good agreement, within the experimental error, with the numerous and coherent experimental data up to about x(Ir) = 0.35. Beyond this value, the agreement is not satisfactory due to the precipitation of solid phases in the liquid.
► So, the In–Ir phase diagram seems therefore to be more complex than the interpolated part from x(Ir) = 0.40 up to 1, and further experimental determinations are therefore needed in the Ir rich part of the phase diagram.