Solute diffusion was measured in the γ-phase, over a wide temperature range, by using the secondary ion mass spectrometric method (with 93Nb, 58Fe and 52Cr) and radiotracer technique (with 95Nb, 95Zr and 59Fe). Linear Arrhenius plots were found for Nb, Zr and Cr diffusion, whereas that for Fe diffusion was quite curved; as in the case of Ti self-diffusion in this compound. The observed solute diffusion behavior was explained in terms of preferential site occupation in the compound, and of interplay between the Ti sub-lattice diffusion mechanism and the inter-sublattice jumps of the solute atoms. Unlike the case of α2-Ti3Al, neither Fe nor Ni diffusion was very fast in the present material. This was attributed to the differing modes of formation of solid solutions (substitutional or interstitial) in the 2 compounds. This, in turn, appeared to be related to the differing Ti atom arrangements around the interstitial octahedral sites in the compounds.

Tracer Solute Diffusion of Nb, Zr, Cr, Fe and Ni in γ-TiAl - Effect of Preferential Site Occupation. C.Herzig, T.Przeorski, M.Friesel, F.Hisker, S.Divinski: Intermetallics, 2001, 9[6], 461-72