INVESTIGATION OF DEFECTS AND ATOMIC ORDERING IN FE72AL28 BY POSITRON-ANNIHILATION AND MOSSBAUER-SPECTROSCOPY

Iron aluminide Fe72Al28 was investigated in states with different defe ct concentrations using the positron annihilation lifetime and Mossbau er spectroscopy methods. The dominant component of 178-187 ps, obtaine d from positron lifetime spectra analysis, corresponds to a high densi ty of vacancies. In the sample where high concentrations of vacancies or dislocations and vacancy clusters were found simultaneously, a seco nd component with a lifetime of 335 ps appears. Mossbauer results show that in the alloy above the Fe3Al stoichiometry concentration the vac ancies prefer to occupy the sublattice in the DO3 superstructure which is reserved for both iron and aluminium atoms. However, this conclusi on 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.