A positron study of the defect structures in the D03 and B2 phases in the Fe-Al system

The positron annihilation technique was used to identify the nature of the vacancy-type defects in the D03 and B2 phases of the Fe-Al system. Seven alloys with Al concentrations in the range 22.7-48 at.% Al and with different thermal treatments were examined. Positron lifetime calculations for the expected defects in the two phases were also performed in order to facilitate the defect identification. In the B2 phase, two types of defects were identified: a thermal complex formed by a Fe-divacancy and an Al antisite, and a Fe-vacancy. No constitutional vacancies were found in the D03 phase.