Investigation of Defects and Atomic Ordering in Fe72Al28 by Positron Annihilation and Mössbauer Spectroscopy

Iron aluminide FeT2Alz8 was investigated in states with different defect concentrations using the positron annihilation lifetime and Mossbauer spectroscopy methods. The dominant component of 178-187 ps, obtained from positron lifetime spectra analysis, corresponds to a high density of vacancies. In the sample where high concentrations of vacancies or dislocations and vacancy clusters were found si~~lultaneously, a second component with a lifetime of 335 ps appears. Mossbauer results show that in the alloy above the Fe3A1 stoichiometry concentration the vacancies prefer to occupy the sublattice in the DO3 superstructure which is reserved for both iron and aluminium atoms. However, this conclusion could not be verified by comparison of theoretical and experimental values of positron lifetimes as the theoretically predicted positron lifetimes for all three types of vacancies are nearly the same.