The Preparation And Characteristics Of Fe₃₆Co₃₆Nb₄Si_4.8B_19.2 Tubes

The progress in bulk soft magnetic glassy alloy has been summed up.Some questions were presented that whether bulk soft magnetic glassy alloys can be prepared under the circumstance of atmosphere and whether obvious GMI effect can be detected in bulk amorphous alloys as the amorphous ribbons and wires can be.In this paper,we choose Fe₃₆Co₃₆Nb₄Si_4.8B_19.2(FeCo-based alloy) alloy,the works of preparation of amorphous tubular alloys,thermal process of samples,measure of magnetic characteristics and structure were completed:1.Series of amorphous tubular alloys with the length of 80～95mm,outer diameter of 2mm and the thickness of 0.1～0.3mm were prepared by copper mounding suction under the circumstance of atmosphere.Besides,the parameters of preparation were investigated.2.Longitudinal GMI effect of as-cast tubes and circular GMI effect of annealed magnetic loop were investigated.The results exhibit that(1) Longitudinal GMI curves of cast-tubes magnetized by the longitudinal magnetic field show a wide flat roof near the zero magnetic field,and the width of flat roof broadened linearly with the increasing of driven frequency; then,the longitudinal GMI curves of cast-tubes magnetized by the circular magnetic field are different.The curves are double peaks when the driven frequencies are below 600 kHz,but the curves are linear when the driven frequencies are beyond the 600 kHz.We believe that the circular direction is the direction of magnetization and the layered magnetic structure leads to the experimental results.(2) the circular GMI of magnetic loop magnetized by circular magnetic field shows that variations of GMI ratio are sensible to the outer circular magnetic field,and GMI ratio enhanced with rising of annealed temperature,especially,the GMI ratio curves,which samples annealed at 540℃temperature,showed the tip GMI as the ribbons of FeCo-based annealed with direct current did.When the driven frequency got to 200kHz,the GMI ratio curves are linear to the value of circular magnetic field near zero magnetic field and the field sensitivity arrived at 1.42%(A·m^-1)^-1.3.A circuit which turns electronic signal to magnetic signal with component of magnetic loop annealed at 540℃was designed.The experimental data shows that the output of voltage is linear to the input of direct current,the linear error is 0.32%,the slow-moving error is 0.41%and the precision error is 1.53%.These data support that the magnetic loops have good linear traits and the soft magnetic materials are excellent materials of magnet sensor.4.The experimental results by XRD show that the composition of phase is still ammorphous,the soft magnetic property change better because of the rearranging and releasing of the inner stress.Then,when the annealed temperature gets to 540℃,the soft magnetic property turns the best as result of appearance ofα-FeCo nano-grains and grow-up in the samples,which made the magnetic domains become lager and coupling of nano-grains stronger.As the annealed temperature went on rising,the hard magnetic phase appears and the magnetic domains were nailed,so the magnetic property and GMI effect decreased sharply.A try on the preparation of bulk glassy alloys under the circumstance of atmosphere were made,and the amorphous tubes of outer diameter 2mm were prepared successfully.Besides, A study on GMI of tubes investigated shows that the circular magnetic property priors to the longitudinal magnetic property.The results anlysed by XRD explained the results of GMI, which do good to know more about the characteristics and microstructure FeCo-based alloys.