The elementary diffusion jump mechanism of Fe atoms in B2 ordered monocrystals (50.5, 55 or 66at%Fe) were determined by means of the quasi-elastic Mössbauer spectroscopy of 57Fe. It was found that the mechanism was the same, regardless of the alloy composition. This mechanism involved jumps into an anti-structure site on the Al sub-lattice, followed by a jump back to a normal site on the Fe sub-lattice. When close to stoichiometry, the Fe atom resided on the anti-structure site for only a small fraction of the time. But, with increasing Fe concentration, and at a sufficiently high temperature, this fraction increased until the residence time on the Al sub-lattice approached the residence time on the Fe sub-lattice. In the case of Fe66Al34, there was no discontinuity in the Mössbauer spectra at the B2  A2 phase transition. It was concluded that this proved that the short-range order decreased continuously in the region of the phase transition.

R.Feldwisch, B.Sepiol, G.Vogl: Acta Metallurgica et Materialia, 1995, 43[5], 2033-9