57Fe Mössbauer spectroscopy and X-ray diffraction were used to study the influence of container internal geometry (flat-endings or round-endings) on the mechanical alloying process of the Fe75Si15B10 system. The Mössbauer spectrum for the sample processed for 19 h in a round-endings container indicates the formation of an amorphous Fe-B-Si phase, with 96% of the Fe total volume. Oppositely, the alloy processed in a flat-endings container for 12 h has a spectrum with 82% of Fe atoms in nanocrystalline Fe,Si and Fe2B phases and the remaining 18% are dispersed at the disordered grain boundary region (amorphous state). This result suggests that a single phase alloy is hard to be obtained in this container. It is also shown that the samples processed in the flat-endings container can be de-mixed to α-Fe phase by milling at times above 18 h. The sample preparation procedures have been repeated twice in order to prove the results reproducibility. © 2006 Elsevier B.V. All rights reserved.