Determination of the activities in the (Ni+Al) alloys in the temperature range 870K to 920K by a solid-state galvanic cell using a CaF2 electrolyte

Abstract The activities of aluminium and nickel are constituents in the (Ni + Al) superalloys in the concentration range 50 mol% to 70 mol% of Al at the temperatures (870, 900, and 920) K were determined with the help of solid-state galvanic cells involving calcium fluoride as an electrolyte. The partial molar Gibbs free energies of aluminium and nickel in the alloys, and the Gibbs free energy of mixing were calculated from the e.m.f. data. The values of the standard Gibbs free energies of formation of the intermetallic compounds NiAl, Ni 2 Al 3 , and NiAl 3 are also given.