It was recalled that much of the previous simulation work on diffusion couples that contained dispersed phases was limited to 1-dimensional models. The models assumed that all of the diffusion occurred in the matrix phase, and that the precipitates were point sources or sinks of solute. Microstructural evolution in the interdiffusion zone, and its effect upon diffusion kinetics, were ignored. The spatial and temporal evolution of 2-phase microstructures was treated explicitly here by using the phase field method. By using a 2-phase diffusion couple as an example, it was shown that the precipitates and the so-called type-0 boundary both migrated as a result of the Kirkendall effect. The type-0 boundary became diffuse, and spread out over several rows of precipitates in the simulation. As a result, the so-called horns in the diffusion path were less sharp than those seen in earlier work, but were similar in that they pointed in the same direction. The initial slope of the diffusion path differed significantly from that in earlier work. The phase field method provided a detailed picture of Kirkendall marker movement in the 2-phase microstructure. The marker plane bent around precipitates, and individual markers moved along curved paths.

Movement of Kirkendall Markers, Second Phase Particles and the Type 0 Boundary in Two-Phase Diffusion Couple Simulations. K.Wu, J.E.Morral, Y.Wang: Acta Materialia, 2004, 52[7], 1917-25