Study On Soft Magnetic Properties And Microstructure Of Fe(Co)NbBCu Nanocrystalline Alloy

As a new type of magnetic functional material, Fe-based soft magneticnanocrystalline alloy with nano-sized grains embedded in amorphous matrixpossesses excellent soft magnetic properties: high permeability, low coercivity andlow core loss. Specifically, Nanoperm with high saturation magnetization andHitperm with high Curie temperature have wide application prospects in magneticelectronics, aerospace, defense, and so on. However, most nanocrystalline alloyscontain too much refractory and easily-oxidized Zr and Hf and Ta elements, as well asnonmagnetic Si element that restricts the saturation magnetization, which result in thecomplex heat treatment process and high production cost, thus seriously limiting theapplication of Fe-based nanocrystalline alloy. In order to solve the above problems,we developed FeNbBCu and FeCoNbBCu soft magnetic nanocrystalline alloys withexcellent soft magnetic properties, and by using VSM, DSC, XRD, TEM and Ramanspectrum measurements, mechanism of crystallization was further studied, theintrinsic correlation between microscopic structure and soft magnetic properties wasrevealed, the Raman spectra characteristic of morphous and annealed Fe (Co) NbBCualloy was measured, which provide a valuable reference for research and applicationof Fe-based soft magnetic nanocrystalline alloy. Main research includes:(1) Based on ternary FeNbB alloy, we developed new Fe83Nb2B14Cu1nanocrystalline alloy with excellent soft magnetic properties and low cost,nanocrystalline grains were refined by minor Cu addition and proper annealingconditions. Mechanism of Cu addition and annealing conditions on crystallizationbehavior, microstructure and magnetic properties were studied, we found that properCu addition promotes the crystallization process. The trend that grain size increasesfirst then decreases and increases again with the increase of annealing temperaturewas discussed by the nucleation and growth mechanism. We found that finemicrostructure is beneficial to decrease magnetocrystalline anisotropy and thereforeoptimize the soft magnetic properties.(2) Based on FeNbBCu alloy, influence of Co element on soft magneticproperties, microstructure and Curie temperature was studied by substituting Fe by Co.We found that the Co addition can obviously increase the saturation magnetization,refine grain size and improve the Curie temperature effectively of the alloy. Byisothermal annealing at about813K for180s, we prepared nanocrystalline alloy with the mean grain size of17nm, high saturation magnetization of1.82T, low coercivityof12A/m, and high Curie temperature of above1200K.(3) The microstructure of Fe (Co) NbBCu amorphous and nanocrystalline alloywas studied by Raman spectrum, it was found that influence of internal crystallizationand structure change on the spectral characteristics is inconspicuous, the internalatomic vibration did not change significantly with the composition or microstructure.