Low Temperature Positron Lifetime and Doppler Broadening Measurements in B2-type FeAl Alloys

ABSTRUCTPositron lifetime and Doppler broadening measurements were carried out at a low temperature, 100K, for B2-type intermetallic compounds FeAl with composition ranges from 41.2 to 50.7 at%Al systematically in order to clarify the feature of lattice defects of the alloys. Quenching temperature dependences of positron lifetimes ranging from 573 to 1173 K was examined for alloys with 41.2, 49.0 and 50.7 at%Al. Two lifetime component analyses could not be made except for a few spectra, indicating a saturation trapping of positrons at atomic vacancies. The mean positron lifetimes are in a range of 175–195 psec, which are not corresponding to vacancy clusters but to mono and/or di-vacancies. The tendency for S-parameter to increase with increase in Al content was found. This suggests that such an increase of S-parameters is attributed to change in the fraction of atoms around the vacancies, not to increase in vacancy concentration.