Effect of boron on structural and magnetic properties of the Fe60Al40 system prepared by mechanical alloying

A new nanostructured system, FeAlB, with high content of boron, was prepared by mechanical alloying in a high-energy ball mill. X-ray diffraction (XRD) and 57Fe Mössbauer spectroscopy were used to study structural and magnetic properties, respectively. Two crystalline phases were found, a majority one corresponding to an FeAl bcc phase and another in low proportion, corresponding to an Fe2B phase type which appears due to the presence of boron. Such a phase is also well observed from Mössbauer spectra. An anisotropic model was applied to fit X-ray patterns, giving evidence of different shapes of the nanocrystalline grains in agreement with the milling process involving both confinement and atomic diffusion. Also it was possible to postulate from both X-ray diffraction and Mössbauer spectrometry that there appears an additional contribution at low hyperfine fields attributed to grain boundaries. This contribution increases as both milling time and boron composition increases.