Concentration fluctuations and thermodynamic properties of ternary liquid alloys

We have reformulated the complex formation model of Bhatia and Hargrove [Phys. Rev. B10 (1974) 3186] such that the extension makes it possible for us to explain the thermodynamic properties of compound forming ternary liquid alloys. The results obtained for the concentration-concentration fluctuations can be used to compute the Warren Cowley short-range order parameter for the same alloy. We make the assumption that a ternary liquid alloy consisting of A, B and C atoms forms complexes A(i)B(j), A(k)C(i), BuCv and A(a)B(b)C(c). Based on this assumption, analytic expressions are derived for such thermodynamic quantities as the free energy of mixing G(M), enthalpy of mixing H-M, the concentration-concentration fluctuations in the long wavelength limit S-cmcn(0) (m, n=1, 2) and the activity, a(i) using the Flory approximation. We solve the derived expressions and thus obtain numerical results for the concentration dependence of these thermodynamic quantities for the ternary liquid Al-Cu-Zr alloys. Finally, a critical discourse of results obtained are given with a view to highlight the information that can be obtained from and limitations of our theoretical model. (C) 2001 Elsevier Science B.V. All rights reserved.