Short-range order in $\alpha$-FeAl soft magnetic alloy

The atomic structure of iron–aluminum alloy samples containing about 7 at % of aluminum ($\alpha$ region of the phase diagram) was investigated by X-ray diffraction. The samples were annealed in the paramagnetic $(T >T_C)$ and ferromagnetic $(T<T_C)$ states. In the first case, the structural state was fixed by quenching from the annealing temperature in water, and, in the second case, by slow cooling. Diffraction patterns of single-crystal samples were taken on an X-ray four-circle diffractometer. It is shown that local ordering, regardless of the prehistory of a sample, is a combination of $B$2-phase clusters (the CsCl type structure), which were previously found in iron–silicon alloys with Si content up to 10%, and small regions with $D0_3$ short-range order. The former consist of two $B$2-cells having a common face, while the latter consist predominantly of one unit cell of the $D0_3$-phase. Within the accuracy of the experiment, no significant difference in the structural states in the paramagnetic and ferromagnetic phases was observed.