Annealed B2-phase samples with Fe contents ranging from 47 to 53at% were studied by using 57Fe Mössbauer spectroscopy. The results were analyzed by using local environment models, according to which point defects in atomic shells close to probe atoms induced shifts in the nuclear monopole interaction. In the case of well-annealed samples, better results were obtained by assuming only the presence of FeAl antisite and VFe vacancy defects, and not that of AlFe antisite defects. The monopole interactions of 57Fe probes on Fe and Al sub-lattices having no defects in the first 2 shells were about 0.27 and -0.03mm/s, respectively, in comparison with data for Fe in -Fe. The shifts which were caused by FeAl and VFe defects in the first shells of Fe probes on the Fe and Al sub-lattices were -0.15 and -0.24mm/s, respectively. In the case of the second shells, the corresponding values were 0.06 and 0.011mm/s. In addition to the structural defects which were required in order to accommodate deviations from stoichiometry, annealed samples were found to contain several percent of FeAl and VFe defects, due to lattice disorder. The latter was greater in Fe-deficient alloys.

G.S.Collins, L.S.J.Peng: Nuovo Cimento D, 1996, 18[2-3], 329-36