The calorimetric investigation of the mixing enthalpy of liquid Co-Ni-Zr alloys at 1873 K

The partial mixing enthalpies of zirconium in liquid Co-Ni-Zr alloys have been determined by means of high-temperature isoperibolic calorimeter. The measurements have been performed along the sections x(Co)/x(Ni) = 3/1, 1/1, 1/3 in the composition range x(Zr) = 0-0.50 at 1,873 K. The values of the partial function are negative over the investigated composition range. The limiting partial enthalpies of mixing of undercooled liquid zirconium in liquid Co-Ni alloys are (-140 +/- 10) kJ mol(-1) (the section x(Co)/x(Ni) = 3/1), (-199 +/- 11) kJ mol(-1) (the section x(Co)/x(Ni) = 1/1), and (-193 +/- 16) kJ mol(-1) (the section x(Co)/x(Ni) = 1/3). The integral mixing enthalpies have been calculated by Gibbs-Duhem integration. The calculated values are mainly negative. The obtained experimental results together with literature calorimetric data have been described by a least square fit using the Redlich-Kister-Muggianu polynomial. The integral mixing enthalpy has been calculated over the entire composition range.