Al versus Si competition in FeSiAl alloys

In FeSiAl alloys, when Si substitutes for Al, important changes take place in the magnetism as well as in the structural properties. Alloys in the two composition series Fe75Al25−xSix (x=0, 7.5, 12.5, 17.5, 25) and Fe70Al30−xSix (x=0, 9, 15, 21, 30) were prepared by induction melting; afterwards they were crushed and then annealed in order to recover the DO3 stable phase. The deformed FeAl samples show larger lattice parameters than the ordered ones; however, this difference (Δa) decreases when Si substitutes for Al until it becomes zero (i.e. until the ordered samples and the deformed ones have the same lattice parameters). This trend is the same for both sample series and does not depend on the Fe content of the alloy. However, the magnetization has a different behaviour depending on the Fe content. For deformed Fe75Al25−xSix alloys the saturation magnetization decreases with increasing Si content while for Fe70Al30−xSix deformed alloys the saturation magnetization has a plateau in which the saturation magnetization values do not vary.