Magnetic and structural studies of ball milled Fe78B13Si9

We report on high-energy ball milling of Fe76B13Si9 alloy prepared from amo rphous and crystallized ribbons as starting materials as well as from a mix ture of pure elemental powders. The X-ray diffraction (XRD), differential s canning calorimetry (DSC), magnetization and Mossbauer measurements were ca rried 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 F e78B13Si9 alloy we obtain two phase mixture of supersaturated alpha -Fe(Si, B) solid solution. The volume fraction of amorphous phase depends on the m illing time. In the case of milling crystalline materials (mixture of cryst alline powders or crystallized ribbon), continuous refinement of the micros tructure was observed. Dissolution of Si and B atoms in Fe lattice during m echanical alloying of elemental powders occurred simultaneously with crysta llite size reduction. The grain size reduction to the nanometer range is ac companied by an increase in atomic-level strain. Decreasing of grain size a nd increasing of the atomic-level strain lead to the decomposition of the F e2B compound during the milling of the crystallized ribbon. Boron atoms dis solve in the Fe crystalline lattice forming supersaturated alpha -Fe(Si, B) solid solution. Similar effect was observed during prolonged milling of me chanically crystallized ribbon. All the alloys studied are ferromagnetic wi th 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 Mossbauer spectroscopy. (C) 2001 Elsevier Science B.V. All rights reserved.