POINT DEFECTS IN FeAl

Point defects in annealed B2-phase FeAl samples in the range 47-53 at.% Fe were studied using 57Fe Mössbauer spectroscopy. Spectra were analyzed using local environment models according to which point defects in atomic shells close to probe atoms induce shifts in the nuclear monopole interaction. For well-annealed samples, better results were obtained assuming only the presence of FeAl antisite and VFe vacancy defects, and not of AlFe antisite defects.. Monopole interactions of 57Fe probes on the Fe and Al sublattices having no defects in the first two shells were about +0.27 and -0.03 mm s-1, respectively, with respect to Fe in alpha-Fe metal. The shifts induced by FeAl and VFe defects in the first shells of Fe probes on the Fe and Al sublattices were -0.134 and -0.31 mm s-1, respectively, and, in the second shells, +0.06 and +0.086 mm s-1. In addition to structural defects needed to accommodate deviations from stoichiometry, annealed samples were found to contain several percents of FeAl and VFe defects due to lattice disorder, with greater disorder in Fe-deficient alloys.