Study On The Modulated Microstructure And Hyperfine Structure Of ALNICO Alloy Under High Magnetic Field

Microstructures of Alnico5 and Alnico8 alloys subjected to isothermal treatment with and without an extermal magnetic field were observed by transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM).The composition of the Fe-Co rich phase and Al-Ni rich phase resulting from spinodal decomposition was studied. Moreover, M(?)ssbauer spectroscopy was utilized to present the parameter of hyperfine field in alloy. And measurements of the magnetic properties were performed on the samples under different treatment.Finally, the process of spinodal decomposition in binary alloy considering elastic energy and treated with magnetic field was simulated using phase-field methed.The microstructure observation results show that, spinodal decomposition take place in Alnico5 alloy when tempered at 830 . The microstructuresprecipitate along the direction of the external magnetic field, the spinodal decomposition gear up and the uniformity of the Fe-Co rich phase particals orientation increases with increasing magnetic field intensities. The extent of Microstructure anisotropism in Alnico8 is greater than Alnico5 both treated without magnetic field. The Fe-Co rich phase particals show great direction consistency with the direction of the 0.7T magnetic field, and become more smaller in 10T magnetic field.Composition analysis shows that the elements Fe and Al Ni Ti enrichto two phases respectively, and Co Cu distribute evenly in Alnico8 alloy after heat treatment. The magnetic field accelerates the element diffusion, when treated in 10T magnetic field, the Fe content increases while the Al,Ni,Ti contents decrease in the Fe-Co rich phase in Alnico8 alloy, moreover there are two Al-Ni rich phases with a large different between composition.M(?)ssbauer spectra analysis shows that the m(?)ssbauer spectra of Alnico5rempering at 830 for 10min can resolve into two ferromagnetic sub-spectra,and Alnico8 three with the same treatment. The shapes of M(?)ssbauer spectra make little difference when Alnico8 is treated without or with 0.7T/10T magnetic field, the average hyperfine field intensity of the alloy decreases a little, while the area ratio between the line 1 6 and the line 2 5 amplifys and the relative area of the sub-spectra corresponding to Fe-Co rich phase increases in the high magnetic field. The simulation results of a binary alloy show that the elastic energy of the alloy has great influence on the modulated structure, there are different structures in homogeneous and inhomogeneous elastic systerms. when treated with a magnetic field, The modulated structure of alloys elongate along the direction of external magnetic field, when observed from the direction perpendicular to themagnetic field, the structures in homogeneous and inhomogeneous elastic systerms keep different.