KINETIC-MODEL FOR INTERMETALLIC-COMPOUND FORMATION DURING INTERDIFFUSION IN A BINARY-SYSTEM

The analysis of experimental data on compound formation during annealing of thin-film and bulk diffusion couples reveals the influence of interface reactions on phase-layer growth kinetics. Based on the mechanism of phase changes during interdiffusion, allowing for the diffusion through the vacancies in the bulk as well as atom travel across the interface and lattice transformations, a model for a phase-layer growth has been developed, in which the rates of the three "elementary" processes are considered to be comparable. In various limiting cases, the model reduces to known theories. The second model, being the extension of the first one to the three-phase case, takes into account an additional equilibrium compound nucleation at a metastable interface of two initial phases. Computer simulation exposed the rate-limiting stages and kinetics of phase-layer thickening, and the influence of the relation between the nucleation and lattice-transformation rates at different interfaces upon new phase formation during interdiffusion in a binary system.