The defects, the behavior of 3d electrons and the hyperfine interactions in binary Fe-Al alloys with diferent Al contents have been studied by measurements of positron lifetime spectra, coincidence Doppler broadening spectra of positron annihilation radiation and Mo¨ssbauer spectra. The results show that on increasing the Al content in Fe-Al alloys, the mean positron lifetime of the alloys increase, while the mean electron density of the alloys decrease. The increase of Al content in binary Fe-Al alloys will decrease the amount of unpaired 3d electrons; as a consequence the probability of positron annihilation with 3d electrons and the hyperfine field decrease rapidly. Mo¨ssbauer spectra of binary Fe-Al alloys with Al content less than 25 at.% show discrete sextets and these alloys make a ferromagnetic contribution at room temperature. The M¨ossbauer spectrum of Fe70 Al30 shows a broad singlet. As Al content higher than 40 at.%, the Mo¨ssbauer spectra of these alloys are singlet, that is, the alloys are paramagnetic. The behavior of a 3d electron and its efect on the hyperfine field of the binary Fe-Al alloy has been discussed.
