Enthalpies of mixing in binary Cu-Eu and ternary Al-Cu-Eu liquid alloys

The enthalpies of mixing in liquid alloys of the binary Cu-Eu and ternary Al-Cu-Eu systems were determined over a wide range of compositions by means of isoperibolic calorimetry in the temperature range 1 300 - 1450 K. The enthalpies of mixing in the Cu-Eu system demonstrate small exothermic effects (Delta H-min = -4.1 +/- 0.5 kJ.mol(-1) at x(Cu) = 0.70). The measurements for the liquid ternary Al-Cu-Eu alloys were performed along five sections (x(Cu)/x(Eu) = 0.70/0.30; 0.50/0.50 and 0.27/0.73 for x(Al) changed from 0 up to 0.30 and x(Al)/x(Eu) = 0.20/0.80 and 0.47/0.53 for x(Cu) changed from 0 up to 0.30). The enthalpies of mixing in the ternary system were found to be exothermic and increasing in absolute values from the Al corner towards the Al0.40Cu0.60-Al0.60Eu0.40 section and from the constituent binary Cu-Eu system towards the same section. The minimum value of the integral enthalpy of mixing is expected in the vicinity of the Al0.6Eu0.4 composition of the binary constituent Al-Eu system (about -23.00 kJ.mol(-1)).