Structure And Magnetic Properties Of Fecunb (ti) Sib

Fe73.5Cu1Nb3Si13.5B9 (trademark Finemet) alloys possesses high saturation magnetization, low coercivity and the eddy current loss is much lower than silicon steel, which is expected to become a widely used new soft magnetic alloys. In this thesis, Fe73.5Cu1Nb3-xTixSi13.5B9(x= 0,1,2,3) amorphous ribbons were prepared by melt spinning technilogy, then subjected to ball milling and isothermal treatments at 500℃and 550℃for 1 h. The effect of Ti content on the crystallization kinetics of amorphous and the effect of annealing temperature and milling time on the micrographs, structure and soft magnetic properties of Fe73.5Cu1Nb3-xTixSi13.5B9(x= 0, 1,2,3) were investigated.Sustaining fine a-Fe(Si) phase is the premise of obtaining excellent soft magnetic properties. It was found that the mixing enthalpy of the Ti doped alloys was lower than the Finemet alloys, the addition of Ti increasing the glass forming ability. The range of the peak temperature,△Tp= TP2-Tp1, increases by doping Ti, which meant that the Ti addition was conducive to the precipitation of a-Fe(Si) phase over a wider temperature region. It can also be inferred that the sample with higher Ti content would precipitate moreα-Fe(Si) phase when annealed at the same temperature.When the Ti content is less than 1%, the amorphous alloys partially crystallized into a singleα-Fe(Si) phase. DO3 superstructure phase precipitates when the Ti content is 2%and above. Heat treatment temperature has a significant effect on the degree of crystallization of amorphous alloys. Ti elements increase the crystallization rate of the samples, improving the magnetic exchange interaction between ferromagnetic phases.The soft magnetic propertiey improves with the Ti content increasing when annealed at 550℃. The coercivity Hc ranged from 3.194 G (x= 0) to 1.151 G (x= 3) and the saturation magnetization Ms ranged from 141.18 emu/g (x= 0) to 149.34 (x= 3) emu/g. Meanwhile, heat treatment temperature rise helps reduce the magnetic anisotropy constant K1, optimizing soft magnetic properties of the alloy.With the increasing of milling time, Fe73.5Cu1Nb3Si13.5B9 alloy powder with the grain size of precipitated been smaller, from 23.6 nm (5 h) to 9.2 nm(40 h). Compared with the direct heat treatment, the grain size of the nanocrystalline precipitated significantly reduced after ball milling.Due to the continued fragmentation of particles during the milling process, the grain boundaries and defects increase, the coercivity He increases as well. The milling time has a great influence on the saturation magnetization and coercivity. Meanwhile, for the same milling time, soft magnetic properties are improved with higher Ti content. After long time milled, coercivity decreases with Ti added. After 60 h milling, He of the non-Ti's sample is 94.323 G, which decreasing to 9.938 G. when the Ti content is 3%. Ms is 133.48 emu/g without Ti element and then increasing to 144.52 emu/g when the Ti content is 3%.