Magnetic and structural studies of ball milled Fe78B13Si9

We report on high-energy ball milling of Fe78B13Si9 alloy prepared from amorphous and crystallized ribbons as starting materials as well as from a mixture of pure elemental powders. The X-ray diffraction (XRD), differential scanning calorimetry (DSC), magnetization and Mössbauer measurements were carried out. High-energy ball milling processes form nanocrystalline Fe-based solid solution for all starting materials investigated. The average grain size was in the range 8–16 nm. By mechanical crystallization of amorphous Fe78B13Si9 alloy we obtain two phase mixture of supersaturated α-Fe(Si,B) solid solution. The volume fraction of amorphous phase depends on the milling time. In the case of milling crystalline materials (mixture of crystalline powders or crystallized ribbon), continuous refinement of the microstructure was observed. Dissolution of Si and B atoms in Fe lattice during mechanical alloying of elemental powders occurred simultaneously with crystallite size reduction. The grain size reduction to the nanometer range is accompanied by an increase in atomic-level strain. Decreasing of grain size and increasing of the atomic-level strain lead to the decomposition of the Fe2B compound during the milling of the crystallized ribbon. Boron atoms dissolve in the Fe crystalline lattice forming supersaturated α-Fe(Si,B) solid solution. Similar effect was observed during prolonged milling of mechanically crystallized ribbon. All the alloys studied are ferromagnetic with Curie temperatures exceeding 850 K independent of a starting materials. The magnetic moments are reduced with increasing milling time. A multiphase composition is also confirmed by Mössbauer spectroscopy.