- In binary systems for which appropriate radioisotopes for both constituents of the alloy are available comprehensive information about the diffusion behavior can be obtained, if both tracer diffusivities are measured in homogeneous alloys of various compositions as functions of temperature. With respect to the Fe-Al system appropriate and inexpensive radioisotopes are available for the Fe component (e.g. âµâ¹Fe) but not for Al. Further insight into the diffusion behavior of Fe-Al intermetallics can also be gained from interdiffusion experiments. In the approach that the authors are suggesting in their paper calculations of the thermodynamic factor Î¦ entering the Darken equation for interdiffusion are carried out. Î¦ is expressed in terms of the energy parameters which describe the ordering process in the binary alloy. Their calculations for Fe-Al alloys show the dependence of Î¦ on the long-range order parameter. These calculations are performed with the energy parameters extracted from the diffuse X-ray scattering data on FeAl. The authors emphasized the influence of the concentration dependences for different temperatures in their calculations. It should be noted that this paper is a continuation of their studies of B2 FeAl thermodynamic factor.