Features of nanocrystallization of metallic glass Fe78B13Si9 induced by high-current-density electropulsing

The microstructure of the nanocrystalline Fe78B13Si9 alloy, prepared by means of high-current-density electropulsing from the parent amorphous alloy (2605S-2), has been investigated by Mossbauer spectroscopy along with X-ray diffraction and transmission electron microscopy. The experimental results show that nanocrystalline Fe78B13Si9 alloy is uniformly composed of the grains about 23 nm in diameter, with an interfacial component. Two crystalline phases are a disordered α-Fe(Si) solid solution with an Si concentration of 11.3 at.% and t-Fe2B. The interface phase is ferromagnetic Fe6.7B4.1Si2.2 with large number of voids, and is estimated to be about 1.3 nm thick with four to five atomic layers. The examination of a comparable isothermally annealed amorphous Fe78B13Si9 sample reveals that the crystalline of the amorphous Fe78B13Si9 alloy and its ultrafine grain structure should be attributed mainly to the electromagnetic effect from high-current-density electropulsing. The mechanism involved is discussed.