The diffusional growth of n compounds, with narrow homogeneity ranges, in a binary system was analyzed. Both constituents were assumed to be mobile. The end-members of the diffusion couple could be any combination of pure elements (when terminal solubility was negligible), saturated terminal solid solutions and binary compounds. The kinetic equations followed from the coupling between chemical reactions at phase boundaries and partitioning of the diffusion flux between 2 adjacent layers. Different kinds of parabolic rate constant were used to describe the growth of compound layers in various conditions, and the relationships between these quantities were established. In particular, the rate constant of the second kind for the exclusive growth of a given compound was a function of the n rate-constants of the first kind measured on the complete couple where all of the intermediate phases grew simultaneously. The rate constant of the second kind was related to the diffusion properties and the thermodynamic stability of the phase. An equivalence between the present approach and the purely diffusional model of Wagner was shown. Most previous models could be retrieved as special cases of this analysis.

On the Diffusional Growth of Compounds with Narrow Homogeneity Range in Multiphase Binary Systems. V.Buscaglia, U.Anselmi-Tamburini: Acta Materialia, 2002, 50[3], 525-35