Magnetic and structural properties of nanostructured Fe–20Al–2Cr powder mixtures

Nanostructured Fe–20Al–2Cr (wt.%) powders have been prepared using high energy planetary ball-mill. Changes in structural, morphological and magnetic properties of the powders during mechanical alloying (MA) and during subsequent annealing have been examined by X-ray diffraction, scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). The observed structural and microstructural changes have been related to several processes occurring during MA. After MA, the material becomes significantly disordered and refines to nanoscale grain sizes (~14nm). The obtained bcc α-Fe(Al,Cr) solid solution shows a ferromagnetic behavior. Upon subsequent annealing at 400°C, α-Fe2O3 and spinel oxides are formed at the surface of particles, while structural defects disappeared as Fe(Al,Cr) solid solution becomes more ordered and grain growth occurs. The saturation magnetization (Ms) shows lower values after annealing, attributed to the formation of metal oxides with low magnetic moment. [Display omitted] •Nanostructured Fe–Al–Cr powders were prepared by MA.•Careful analysis of the XRD patterns by using the Rietveld refinement•The lattice distortion is evidenced by the increase of both the lattice parameter and the static Debye Waller parameter.•Annealing at 400°C stabilizes the microstructure at the nanometer range and leads to the formation of Fe3O4 and Fe2O3 oxides.•Both the milled and annealed samples are ferromagnetic.