Magnetic, structural and thermal properties of the Finemet-type powders prepared by mechanical alloying

The mechanical alloying process has been used to prepare nanocrystalline Fe73.5Si13.5B9Nb3Cu1 powders in a high energy planetary ball-mill Retsch PM400/2. Morphological, microstructural, structural, thermal and magnetic characterizations of the powders milled several times were investigated by scanning electron microscopy, X-ray diffraction, differential scanning calorimetry and hysteresis meter. A mixture of Fe(Si)-type nanograins (14 nm), Fe2B boride phase (∼12 nm), and bcc substitutional Fe(B)-type solid solution is obtained after 150 h of milling. The coercivity and saturation magnetization values are about 62 Oe and 14 emu/g, respectively. Several magnetic transition temperatures are revealed in the DSC scans of the ball-milled powders in the temperature ranges 500–560 °C and 599–606 °C, related to the Fe(B) and Fe(Si)-type phases, respectively.

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► Nanostructured Fe73.5Si13.5B9Nb3Cu1 Finemet powders were prepared by MA.
► Analysis of the XRD patterns by using the Rietveld refinement.
► The formation of Fe2B boride, Fe(B)-type and Fe(Si)-type solid solutions are achieved after 150 h of milling.
► Several magnetic temperature transitions are revealed in the DSC scans.
► The distribution of Si, B and Nb atoms in the Fe lattice leads to the heterogeneity of the Finemet powders.