Study of Fe-Ni alloys produced by mechanical alloying

Fe1-xNix samples with 0.225 <= x <= 0.400 were prepared by mechanical alloying. XRD studies showed that this group of samples presents the bee and fee phases in all the composition ranges. The variation of the lattice parameter, a, of the two phases as a function of the Ni content, remains independent of the composition. In this case all Mossbauer spectra were fitted using a hyperfine field distribution (HFD). Samples between 22.5 and 32.5 at% Ni present a paramagnetic site. For sample with 25 at% Ni, it was used an additional sextet to obtain a good fit. From the Mossbauer fitting in the field distributions, besides the field associated to the bcc and fcc microcrystalline phases (between 30 and 33 T), additional peaks at smaller fields can be noticed (between 10 and 27 T). These small fields can be associated with the contribution of those Fe magnetic sites localized in the surface and interfaces of the grains. This contribution is postulated as a consequence of the nanometer size of the bee and fee grains obtained by DRX. (c) 2006 Elsevier B.V. All rights reserved.