Interfacial adsorption in ternary alloys

Interfaces of A-B-C ternary alloys decomposed into two and three phases are studied. The effect of the gradient energy coefficients κ_II, I = A, B, C, on the interface composition profiles of ternary alloys is examined. The adsorption of component C in ternary alloys is obtained numerically by finding steady-state solutions of the nonlinear Cahn-Hilliard equations and by solving the two Euler-Lagrange equations resulting from minimizing the interfacial energy, and analytically near the critical point. It is found that the solutions from both numerical methods are identical for a two-phase system. In symmetric ternary systems (equal interaction energy between each pair of components) with a minority component C, the gradient energy coefficient of C, κ_CC, can have a very strong influence on the degree of adsorption. In the α and β two-phase regions, where α and β are the phases rich in the majority components A and B, respectively, as κ_CC increases, the adsorption of the minority component C in the α and β interfaces decreases. Near a critical point, however, the degree of adsorption of minority component C is independent of the gradient energy coefficient.