Magnetic hardening of FeSiBCuNb ribbons and wires during the first stage of crystallization to a nanophase structure

The structural and magnetic properties of Fe73.5Si 13.5B9Cu1Nb3 alloy wire and ribbon have been studied after thermal treatments up to temperatures at which partial (75%) devitrification to a nanocrystalline structure occurs. Nanocrystals are detected by x-ray diffraction only after treatments around 500°C, while differential scanning calorimetry studies suggest that substantial structural change is inititiated at a much lower temperature (about 400°). A clear magnetic hardening is observed in samples heated within the temperature range 400-480°C. This phenomenon is also accompanied by an increase of the linear magnetostriction. These effects are discussed in terms of the local structural rearrangements produced during the first stages of the crystallization process. The study is also extended partly to FeSiB, FeSiBCu, and FeSiBNb alloys