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

Abstract

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.