Thermodynamic properties of alloys of the Al—Co and Al—Co—Sc

Abstract

Mixing enthalpies of melts of the binary Al—Co system at 1870 К in the range 0 < xCo< 0,25, and at 1620 K, 0 < xCo < 0,12 were investigated by the isoperibolic calorimetry. Mixing enthalpies of melts of the ternary Al—Co—Sc system were investigated at 1870 К for the sections Al_0,75(1-x)Co_0,25(1-x)Sc_x, 0 < х < 0,024, і Al_0,88(1-x)Co_0,12(1-x)Sc_x, 0 < х < 0,044. Using the data from literature on the mixing enthalpies of liquid an solid alloys, activities of the components of melts, and the phase diagram of the Al—Co system, by means of the calculating program package created by us, based on the model of ideal associated solutions, the thermodynamic properties of liquid and solid alloys of the Al—Co system in the wide range of temperature at any composition were calculated Mixing enthalpies and liquidus surface of the phase diagram of the ternary Al—Co—Sc system in the whole concentration interval were estimated by modeling from the data for the binary boundary subsystems. All the components of both binary Al—Co and ternary Al—Co—Sc systems show a tendency to interact with each other rather strongly: ΔН_min(АІ—Со) = -32,5 kJ/mole at х_Со = 0,44; ΔН_min(Al—Co—Sc) = —46 kJ/mole for Al_0,4Co_0,3Sc_0,3(estimation).