The influence of Al content on the relaxation peaks in quenched Fe-Al alloys

The influence of the Al content on the two relaxation peaks (P1 and P2) in quenched Fe-Al alloys has been investigated using a multifunctional internal friction apparatus. It has been shown that the Al content has a significant effect on the two peaks and their relaxation strength varies non-monotonically with the Al content. The variation of the relaxation strength results from the changes of the properties and the concentrations of atomic defects with the Al content. The peak P1 originates from the reorientation of di-vacancies on nearest neighbor Fe-sublattice sites. The peak P2 is associated not only with vacancies but also with antisite atoms. The relaxation strength of P1 has a maximum in the vicinity of 23 at.%Al and it declines rapidly when the Al content is over 23 at.% because of gradual reduction of the concentration of di-vacancies with increasing the Al content. The peak P2 does not appear in alloys with less than 23 at.%Al. Its relaxation strength keeps roughly constant in the range of Al contents from 23 to 38 at.%, in which antisite atoms can be formed because of ordering and the number of vacancies at a site (Fe sublatices in B2 structure for Fe-Al alloys) does not change very much