Abstract The magnetic and structural properties of the nanostructured system Fe 1–x Si x with x = 0.1, 0.2 and 0.3 were studied by X‐Ray diffraction (XRD), SEM, and Mössbauer Spectrometry (MS). The samples were prepared by compacting and sintering at two temperatures, 900 and 1000 °C, from powders obtained by means of two procedures: by elemental mixing of Fe and Si powders and by mechanical alloying (MA). For samples obtained from mixed powders and sintered at 900 and 1000 °C, XRD and MS show the presence of pure iron and silicon, indicating that these conditions do not favor alloying, except for the sample with 30 at.% and 1000 °C, for which, besides of iron and silicon patterns, the DO 3 and FeSi phases are also evidenced. The grain sizes are approximately ranged from 24 to 40 nm for the pure iron and 43 to 90 nm for the pure silicon. For the mechanical alloyed powders, the as milled samples with 10 and 20 at.% Si consist of a bcc structure and for 30 at.% of FeSi and DO 3 phases. The grain sizes are 14, 12 and 7 nm for 10, 20 and 30 at.% Si, respectively, showing that the fragility increases with silicon content and for the as sintered sample with 10 at.% Si BCC grain size is now approximately 15 nm. It is worthy to note that when sintering, the DO 3 , FeSi and Fe 5 Si 3 phases are developed, while in the 30 at.% Si as sintered mixed elemental powder, only an incipient alloy is obtained. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)