Effect of the Milling Conditions on the Formation of Nanostructured Fe–Al Powders
Nanocrystalline Fe72Al28 alloy samples were prepared by the mechanical alloying process using planetary high-energy ball mill. The alloy formation and different physical properties were investigated as a function of milling time, t, (in the 0-24 h range) by means of the X-ray diffraction (XRD) technique, scanning electron microscopy (SEM), energy dispersive X-ray (EDAX) and Mössbauer spectroscopy. The complete formation of bcc-FeAl solid solution is observed after 4 h of milling. The lattice parameter, a (nm), quickly increases within the first hours of milling and reaches a maximum value of 0.291 nm at 12 h of milling time; then a (nm) decreases to a value of 0.2885 nm for 24 h. The grain size decreases from 55 to 10 nm, while the strain increases from 0.18% to 0.88%. Grain morphologies at different formation stages were observed by SEM. The Mössbauer spectra show different behaviors with the increase of milling time. Indeed, after 4 h, the Mössbauer spectrum shows the presence of a singlet and sextet. The singlet indicates the presence of paramagnetic phase characteristic of A2 disordered structure and the sextet with a mean hyperfine field, , of 21 T is indicative of ordered DO3 structure. After 8 h of milling, the paramagnetic phase disappears leading to the appearance of a sextet, with a mean hyperfine field, Hhf, equal to 24.18 T which is characteristic of DO3’ structure. For the higher milling time i.e. 24 h, the Mössbauer spectrum was analyzed with two components. The first one with equal to 29.9 T is still indicative of ordered DO3, however, the second with a value of 10.25 T is characteristic of the fine domain B2 ordered structure.
Z. Hamlati et al., "Effect of the Milling Conditions on the Formation of Nanostructured Fe–Al Powders", Advanced Materials Research, Vol. 214, pp. 490-497, 2011