A model for diffusion in ordered phases having the B2 body-centered cubic structure was developed and was generalized to multi-component alloys. The model used thermodynamic data to evaluate the thermodynamic factor, as well as the degree of ordering at a given temperature. The activation energy for diffusion was expressed as a function of the degree of order. The available experimental data for the present systems were considered, and some inconsistencies in the data for the Al-Fe system were pointed out. The practical use of the model was demonstrated by performing a computer simulation of a diffusion experiment. The results of the simulation agreed well with experimental observations.

A Phenomenological Treatment of Diffusion in Al-Fe and Al-Ni Alloys having the B2-BCC Ordered Structure. T.Helander, J.Agren: Acta Materialia, 1999, 47[4], 1141-52