Investigation On Magnetic Properties Of Nanocrystalline Fe-Co-Cu-Nb-Si-B Soft Magnetic Alloys

Nanocrystalline Fe_73.5Cu₁Nb₃Si_13.5B₉ alloy is a very attractive soft magnetic material exhibiting excellent permeability, high Curie temperature while maintaining low core loss. Now it has been widely applied to kinds of transformer, mutual inductance and so on, and has achieved good results. With the development of modern technology of electron and information, new demands of soft magnetic material arise, which include requiring the part's smaller volume, greater power, higher working temperature or frequency. We added Co to Fe_73.5Cu₁Nb₃Si_13.5B₉ alloy, and get (Fe₅₀Co₅₀)_73.5Cu₁Nb₃Si_13.5B₉ alloy. No investigation on the alloy has been made at home and abroad.Amorphous (Fe₅₀Co₅₀)_73.5Cu₁Nb₃Si_13.5B₉ alloy were prepared by single roller method. Amorphous structure was identified by means of X-ray diffraction. Crystallization temperature of amorphous alloy was measured by a differential scanning calorimeter (DSC), then the range of annealing temperature was determined. Different grain size nanocrystalline alloy were obtained by annealing at different temperature. Soft magnetic properties of nanocrystalline (Fe₅₀Co₅₀)_73.5Cu₁Nb₃Si_13.5B₉ alloy were investigated focusing the following aspects.First, the structure of (Fe₅₀Co₅₀)_73.5Cu₁Nb₃Si_13.5B₉ alloy annealed at different temperature was studied. Microstructure and averaging grain size were analysed by X-ray diffraction and scan electron microscope. The results show that when annealed at 460℃the alloy has crystallized , the average grain size is about 20nm, which will become bigger with increasing annealing temperature.Second, we studied room temperature magnetic properties of (Fe₅₀Co₅₀)_73.5Cu₁Nb₃Si_13.5B₉ toroidal core sample, including the characteristic of static and frequency spectrum. We found that excellent static soft properties can be obtained for (Fe₅₀Co₅₀)_73.5Cu₁Nb₃Si_13.5B₉ annealed at 460℃. Based on frequency spectrums, we studied quality factor, and cut-off frequency as a function of annealing temperature, as well as core losses. The results show that cut-off frequency of nanocrystalline of (Fe₅₀Co₅₀)_73.5Cu₁Nb₃Si_13.5B₉ alloy is much higher than Fe_73.5Cu₁Nb₃Si_13.5B₉.At last, we conducted a thorough investigation into magnetic properties of the samples in high temperature environment. Change of initial permeabilityμ_i with temperature, change of permeabilityμunder different magnetic density field with temperature, and frequency spectrum in high temperature were studied.. Addition of Co greatly enhanced Fe_73.5Cu₁Nb₃Si_13.5B₉ alloy soft magnetic properties when used in high temperature condition.