Short-Range Order in α-FeAl Soft Magnetic Alloy

Resumo

The atomic structure of iron–aluminum alloy samples containing about 7 at % of aluminum (α 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 B2-phase clusters (the CsCl type structure), which were previously found in iron–silicon alloys with Si content up to 10%, and small regions with D0₃ short-range order. The former consist of two B2-cells having a common face, while the latter consist predominantly of one unit cell of the D0₃-phase. Within the accuracy of the experiment, no significant difference in the structural states in the paramagnetic and ferromagnetic phases was observed.