Structural properties of Fe50Co50 nanostructured powder prepared by mechanical alloying

Mechanical alloying of high purity elemental powders in a planetary ball mill (Fritsch pulverisette 7) was used to prepare nanocrystalline Fe and equiatomic FeCo powders. Morphology changes, structural properties and local iron environment variations have been investigated by Scanning Electron Microscopy, X-ray diffraction and Fe-57 Mossbauer spectrometry. X-ray diffraction profile fitting, reveals the Co allotropic transformation from fcc to hcp form at the early stage of milling. The milling route implies diffusion of hcp-Co into alpha (Fe) leading to the formation, after 12 h, of the bcc-FeCo solid solution with a lattice parameter close to a = 0.2861 nm and a grain size of about 12 nm. The analysis of the evolution of the hyperfine magnetic field distribution, indicates that the disordered bcc-FeCo solid solution is formed after 12 h of milling, through the interdiffusion of Fe and Co elemental powders. The average hyperfine magnetic field of the bcc-FeCo solid solution (B = 35 T) suggests that the disordered Fe50Co50 system is formed. (C) 2004 Elsevier B.V. All rights reserved.