| The magnetic navigation positioning system can be used in the radiofrequency ablation technology to avoid invalid damage during the operation,which can increase the validity,stability and safety of the ablation procedure.The sensitivity and accuracy of the magnetic navigation positioning system is significantly dependent on the soft magnetic properties of the magnetic core materials.In addition to the excellent mechanical properties and corrosion resistance,Co based amorphous alloys exhibit high magnetic permeability,low coercive force and high saturation magnetic induction,which are the excellent soft magnetic materials to prepare the magnetic core of the magnetic navigation positioning systems in the radiofrequency ablation technology.Therefore,In the present thesis,the Co46Fe20B23Si5Nb6 alloys with good soft magnetic properties was taken as the research object,and the amorphous forming ability and soft magnetic properties of Co46Fe20B23Si5Nb6 alloys were optimized by adjusting the ratio of Fe/Co.Moreover,the effects of the preparation process and the heat treatment on the microstructure and magnetisms of the Co-based alloy were investigated.The aim of the work is to developed the magnetic core materials with the excellent soft magnetic properties for magnetic navigation positioning system for Hunan APT Medical Devices Company.The main research contents and results of the paper are as follows:(1)The effect of the ratio of Fe/Co on the amorphous forming ability and soft magnetic properties of Co(46+x)Fe(20-x)B23Si5Nb6 alloys was studied.The results show that,the Co(46+x)Fe(20-x)B23Si5Nb6 alloys with Fe content of 16%exhibit the relative high amorphous forming ability and thermal stability,evidenced by its wide supercooled liquid region(ATX)of 40.80?.Moreover,the Co50Fe16B23Si5Nb6 amorphous alloy shows the good magnetic properties with a saturation magnetization of 80.96 emu/g and coercive force of 20.53 G.(2)The Co50Fe16B23Si5Nb6 amorphous alloy was prepared by rapid cooling on a single cooper wheel,copper-mold suction casting and melt extraction technique.And the effects of cooling rate on the thermodynamic properties and soft magnetic properties of Co50Fe16B23Si5Nb6 alloy were studied.It is found that increasing the cooling rate can promote the glass transition temperature(Tg),supercooled liquid region(?T)and the enthalpy of the subcooled liquid region(AH),but decrease the saturation magnetization and the coercivity decrease of the amorphous alloy.(3)The Co50Fe16B23Si5Nb6 alloys were annealed at different temperatures,and the effects of the annealing temperature and time on the microstructure and soft magnetic properties of amorphous alloys were investigated.The results show that the alloys remain the amorphous state after annealed at 570 and 620?.The soft magnetic properties of the amorphous alloy are improved due to the release of the internal stresses in the as-cast alloy during the anealing treatment.Partially crystallization ocurrs in the amorphous alloy with the precipitates of the Fe23B6 phases in the amorphous alloy after annealed at 700?.With the annealing temperature further increases to 800?,the complete crytallization ocurrs in the alloy to produce crystallites of Fe23B6,Fe2B and Fe3Si.The presence of the crystallites and their growth deteriorate the soft magnetic properties of the alloys.The alloy annealed at 620? for 5 min exhibits the improved soft magnetic properties,evidenced by its relative low coercive force(0.61 G)and high saturation magnetization(84.26 emu/g). |
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