Study On The Microstructure And Properties Of Fe-M-Si-Cu-B Amouphous Magnetic Materials

Due to the excellent soft magnetic properties,Finemet alloy has been widely used in many areas,such as current transformer,inverter power supply,and so on.Since the rapid quenching of alloy is always processing in the atmosphere and the equipments typically lose stability in practical production,the oxidation and defects,e.g.,the surface with bad quality,brittle melt-spun,often occur on the free surface of the alloy,which will worsen its magnetic properties.Moreover,Finemet is expensive because of the high cost of its constituent Nb element.In this study,the principles of the production of the defects during melt-spinning and the corresponding prevention methods have been studied using the X-ray diffractometer,the measuring instrument of soft magnetic properity,transmission electron microscope,scanning electro microscope and vibrating sample magnetometer.Through the addition of amorphous ribbions in the re-melting process,the effect of the addition quantity of amorphous ribbions on the properties of as-spun ribbons has been investigated.In addition,the consitituent element Nb was replaced by V which is cost-effective,and then the annealing process and the relationship between the miscrostructure and magnetic properities have been studied.The results show that the as-spun ribbions of Finemet have poor soft magnetic properities and high iron loss because of the existence of magnetocrystalline anisotropy.The magnetic properities of as-spun ribbons improve significantly after annealing.When annealed at 550?,the ribbons achieve their best comprehensive magnetic properties of Bs=1.186 T,?_i=137 k,Hc=0.58 A/m and P_0.5/20k=24.39 W/kg.The content of Fe_73.5Cu₁Nb₃Si_13.5B₉ ribbons influences the properties of Fe_73.5Cu₁Nb₃Si_13.5B₉+N%Fe_73.5Cu₁Nb₃Si_13.5B₉ ribbons fabricated by melt-spinning with a wheel speed of 25 m/s.With the increases of the addition quantity of amorphous ribbons,the number of the short-range ordered structures increase and the stability of ribbons decreases,which is advantageous to achieve a high proportion of crystalline phase.Fe_73.5Cu₁Nb₃Si_13.5B₉+N%Fe_73.5Cu₁Nb₃Si_13.5B₉ ribbons consist of?-Fe₃Si and amorphous phase.The best comprehensive soft magnetic properties of Fe_73.5Cu₁Nb₃Si_13.5B₉+25%Fe_73.5Cu₁Nb₃Si_13.5B₉ribbons are obtained after annealed at 550?for one hour,which are Bs=1.32 T,Hc=0.42A/m,?_i=162 k and P_0.5/20k=19.36 W/kg.The addition of V element could reduce the stability of Fe_73.5Cu_1.5Nb_3-xV_xSi_13.5B_8.5?x=0,1,2,3?ribbons and improve the ductility.However,the ribbons have a poorer oxidation resistance than Nb-added ribbons.After annealed at 540?for one hour,Fe_73.5Cu_1.5Nb₂V₁Si_13.5B_8.5 ribbons achieve the best comprehensive magnetic properties of Bs=1.35 T,Hc=0.57 A/m,?_i=168 k,P_0.5/20k=25.2W/kg.