The development of an accurate thermodynamic model description for the Fe–Al–Cr system was hampered by the sparseness of thermodynamic data on this system. This compelled measurement of the Fe–Al–Cr system by using the Knudsen effusion mass spectrometry technique. Two samples with target compositions of 45.1Fe–39.8Al–15.1at%Cr and 49.9Fe–19.9Al–30.2at%Cr were investigated at 1150 to 1550K. These measurements were combined with a revised thermodynamic model description for this system, based upon the so-called Calphad approach. This approach permitted the prediction of thermodynamic properties in the ternary system from the Gibbs energy formulations of the binary sub-systems. This combination was used to discriminate between the quality of the sparse experimental activity data available in the literature and the present experimental data. It was found that additional iron activity measurements were necessary in the Fe–Al binary system. Additional activity measurements of iron, aluminium and chromium were also necessary in a compositional region close to this system. Preliminary calculations were made of the on-diagonal thermodynamic factors; which appeared to be largest in the compositional region close to the system Fe–Al. For a composition in the ternary system they decreased in the order: Al, Fe, Cr.

Thermodynamics and Diffusion in Ternary Fe–Al–Cr Alloys, Part I - Thermodynamic Modelling. M.H.G.Jacobs, R.Schmid-Fetzer, T.Markus, V.Motalov, G.Borchardt, K.H.Spitzer: Intermetallics, 2008, 16[8], 995-1005