Crystallization of Co-containing Finemet alloys

Fe73.5−xCoxSi13.5B9Cu1Nb3 (x=13.5 and 60 at.%) materials with different volumetric fractions of nanometer-sized (Fe, Co)Si crystallites produced by controlled crystallization of the amorphous alloy, were studied by combining 57Fe Mössbauer spectrometry (MS) and X-ray diffraction (XRD). The crystalline fractions were first estimated and the compositions of both the amorphous residual phase and the nanocrystalline phase were modelled. The composition of the (Fe, Co)Si nanosized crystals does not change with the crystalline fraction but depends on the amorphous composition. Lattice parameters, hyperfine fields and Curie temperatures data are consistent with the proposed composition.