Vacancy-type defects in the B2-type intermetallic compound were investigated as a function of compositions ranging from 41.2 to 50.7at%Al, and quenching temperatures ranging from 610 to 1373K, by using positron annihilation techniques. At quenching temperatures lower than 873K, both the mean positron lifetimes and S-parameters increased with increasing Al content. With increasing quenching temperatures above 873K, the S-parameters for 41.2, 49.0 and 50.7at%Al increased. The results were explained by considering changes in defect type, and the atomic configuration around vacancies. The compositional dependence at lower quenching temperatures was attributed partly to a change in the fractions of Fe-vacancies (VFe) and di-vacancies on the Fe-sites (2VFe) and partly to a change in the fraction of antisite Fe atoms (FeAl). A temperature dependence of the S-parameter was explained by a change in defect type from di-vacancies (2VFe) to various types of di-vacancies (VFeVAl) sitting on nearest-neighbour Fe and Al sites.

A Study of Vacancy-Type Defects in the B2-Phase Region of the Fe–Al System by the Positron Annihilation Method. T.Haraguchi, F.Hori, R.Oshima, M.Kogachi: Intermetallics, 2001, 9[9], 763-70