Connections between thermodynamic quantities and vacancy and diffusion characteristics in binary metallic solid solutions

Abstract

With the use of the similarity of interatomic potentials relations concerning vacancy and diffusion characteristics in disordered regular solid solutions have been derived. It has been shown that the vacancy concentration is constant along ifTc(x) = TA + (TB − TA)x + 2ΔTx(1−x), (TA and TB are the melting points of pure components A and B respectively, and ΔT is proportional to the excess enthalpy of mixing, x is the concentration of the atoms B) which is proportional to the binding energy of the crystal. The validity conditions of several empirical rules known in the literature are also analyzed. It has been found that the generalization of the well-known rule for self- and impurity diffusion in pure metals has the following form In D0z(x) ∼ pQz(x)Tc(x) (Z = AorB) where p is a constant for alloys having identical structures (D0z(x) and Qz(x) denote the preexponential factors and the activation energies respectively). The results calculated from the relations derived were compared with experimental data for tracer diffusion in the systems AgAu, CuNi (having slight deviation from regularity), Pb-Tl (showing ordering phenomena) and AlZn (clustering effects) and a good agreement was found.