Study On The Properties And Preparation Of Fe-based Magnetostrictive Fibers

Fe80B20 amorphous fibers and Fe79-xB20NbxCu1(x=0,2,4,6,8) amorphous fibers were prepared by the single roller melt-spinning method. After annealed,the Fe80B20 fibers were investigated by X-ray diffractometer(XRD), scanning electron microscopy(SEM), differential scanning calarmeutry(DSC), vibrating sample magnetometer(VSM) and impedance meter. Effect of annealing process on the structure and properties of those fibers were discussed. The fibers with excellent soft magnetic and magnetostrictive properties were obtained by the suitable annealing treatment.In this study, Fe80B20 amorphous fibers were firstly prepared by the single roller melt-spinning method under the condition of rotating speed of 2400 r/min.The effects of annealing temperature on the structures and magnetic properties of the fibers were investigated. The result of DSC shows that the crystallization temperature of the fibers is 449 oC at a heating rate of 60 oC/min. The crystallization activation energy was calculated to be 221 kJ/mol using Kissinger formula. The SEM images show that a few dendrites appear at the fiber surface after annealing, which is confirmed to be Fe3 B phase. The XRD patterns show that the as-spun fiber is amorphous. And the fiber is still amorphous when the annealing temperature is lower than 400 oC, but crystallization after annealed at500 oC. The result of VSM indicate that the fibers have strong magnetic anisotropy by the difference between hysteresis loop of fibers measured in magnetic field parallel and perpendicular to the fiber axis. With the increase of the annealing temperature, the coercivity of the fibers increase, and the coercivity is the highest when the annealing temperature is 500 oC. Finally, the resonance behavior and quality merit factor(Q value) of the fibers were characterized for magnetostrictive sensors. With the increase of annealing temperature, the Q value increase firstly and then decrease, and finally increase to about 2000 after annealed at 500 oC.In order to improve the soft magnetic property of fibers, Cu and Nb were added in Fe79-xB20NbxCu1(x=0,2,4,6,8) fibers, which prepared by the singleroller melt-spinning method. To improve the magnetic property of Fe-B-Nb-Cu fibers, the nanocrystalline fiber is obtained by annealing treatment. The result of DSC shows that Cu has no effect on the crystallization temperature of Fe79-xB20 Nbx Cu1(x=0,2,4,6,8) fibers. With the increase of Nb content, the crystallization temperature increase. The result of VSM indicate that Cu and Nb improve the soft magnetic property of fibers. Effect of annealing temperature and time on the magnetic property of Fe77B20Nb2Cu1 fibers. After annealed at570 ? for 5 min, the Fe77B20Nb2Cu1 nanocrystalline fibers exhibit excellent soft magnetic property.