Physico-chemical analysis of compound growth in a diffusion couple with two-phase end-members

A general treatment of a diffusion-controlled growth of a stoichiometric intermetallic in reaction between two two-phase alloys is introduced. A reaction couple, in which a layer of Co2Si is formed during interdiffusion from its adjacent saturated phases is used as a model system. On the basis of chemical reaction equations occurring at the interphase interfaces, data on relative mobilities of diffusing species and the integrated diffusion coefficient in the product phase are deduced. The analysis yields numerical results identical to those calculated from classical Wagner's theory for the case in which the terminal phases of the diffusion couple are initially saturated.