Calorimetric investigation of mixing enthalpy of liquid (Co + Cu + Zr) alloys at T = 1873 K

•The mixing enthalpies of liquid (Co + Cu + Zr) alloys have been investigated with high-temperature calorimeter at T = 1873 K.•The experimental results have been fitted using Redlich–Kister–Muggianu polynomial.•The isoenthalpic curves have been constructed in the entire composition range.•Toop and Kohler extrapolation models have also been used for the calculations.

The enthalpies of mixing of liquid (Co + Cu + Zr) alloys have been determined using the high-temperature isoperibolic calorimeter. The measurements have been performed along three sections (xCo/xCu = 3/1, 1/1, 1/3) with xZr = 0 to 0.55 at T = 1873 K. Over the investigated composition range, the partial mixing enthalpies of zirconium are negative. The limiting partial enthalpies of mixing of undercooled liquid zirconium in liquid (Co + Cu) alloys are (−138 ± 18) kJ · mol−1 (the section xCo/xCu = 3/1), (−155 ± 10) kJ · mol−1 (the section xCo/xCu = 1/1), and (−130 ± 22) kJ · mol−1 (the section xCo/xCu = 1/3). The integral mixing enthalpies are sign-changing. The isenthalpic curves have been plotted on the Gibbs triangle. The main features of the composition dependence of the integral mixing enthalpy of liquid ternary alloys are defined by the pair (Co + Zr) and (Cu + Zr) interactions.