Study On The Influence Of Key Technology Of Preparation On The Magnetic Properties And Microstructure Of 2:17-type SmCo Permanent Magnets

2:17 SmCo permanent magnetic materials have been widely used in aerospace and other special fields because of their excellent heat stability and corrosion resistance.However,because of their low magnetic energy product,it has become an important defect of this kind of magnets.In this paper,the relationship between the technologies and magnetic property and microstructure of 2:17 SmCo permanent magnetic materials is studied.These technologies include melting process,sintering-solid solution and aging process.The effects of different processes and formulations on the magnetic properties,microstructure and precise elements of2:17 SmCo magnets are analyzed.The best magnetic properties in this process and the best process are given by the paper.The main contents of this paper are as follows:1.The effects of melting process on the magnetic properties,microstructure and phase transformation process of 2:17 SmCo alloy are studied.The magnetic properties of the melted 2:17 SmCo alloy are as follows:remanence Br=0.038 T,intrinsic coercivity H_cj=170.3 Am²/kg,maximum magnetic energy product?BH?_max=0.110 MGOe.The value is much lower than that of the practical magnet.It indicates that the magnets do not form the required phases and microstructure.The samples mainly include SmCo 2:17R phase,SmCo 2:17H phase and SmCo₅ phase,as well as bits of SmCo₂ phase,SmCo₃ phase and SmO_x phase.The surface structure of the alloy ingot is uneven.The inner of the alloy ingot is more uniform.In the process of preparation,the cooling rate of the inner and outer parts of the alloy is different,which leads to the difference of the composition.The Sm content in the alloy is volatilized in the smelting process.The fraction of Sm in the alloy is reduced from 25.59 wt%to 20.19 wt%after melting.The other elements Co,Zr,Fe and Cu elements have little change;the DSC analysis of 2:17 SmCo alloy shows that the DSC curve reaches a peak at 823?.The theoretical study shows that the point is the phase transition temperature point between the SmCo 2:17R phase and 1:5 phase and a new phase is generated.2.The effects of formula,solid solution and sintering process on the magnetic properties and microstructure of 2:17 SmCo alloy are studied.The 2:17 SmCo magnets with different Fe were tested at different sintering temperatures.The optimum sintering temperature is 1215?and the optimum Fe content is 15.5 wt%.With the increase of Fe content,the diffraction peak intensity of2:17R phase shows an increasing trend as a whole.But the intensity of Fe content of17.5 wt%and 19.5 wt%decreases.The peak intensity of 1:5 phase also increases as a whole.The maximum magnetic energy product?BH?_max=29.38 MGOe was obtained when the 2:17 SmCo alloy was dissolved at 1185?for 8h.The remanence B_r increases first and then decreases with the time extension.The intrinsic coercive force H_cjj increases first and then decreases with the time extension.The optimum maximum magnetic energy product?BH?_max=28.94 MGOe.B_r,H_cjj and?BH?_maxax all increases with the increase of sintering temperature,and the sintered alloy ingot at1215?for 1 h had no characteristic crystal cell structure.The content of Sm element in 2:17 SmCo alloy is measured by a fluorescence spectrometer.The Sm element volatilizes after solid solution and sintering,and the mass fraction decreases from 25.59 wt%to 17.04 wt%and 16.93 wt%respectively.3.The effect of isothermal aging process on the magnetic properties and microstructure of 2:17 SmCo alloy is studied.The isothermal aging time study shows that 2:17 SmCo alloy has the maximum magnetic energy product?BH?_max=29.59 MGOe at 840?for 5 h.And the B_r and the H_cjj decrease with the time extension.The SEM images of different aging time show the complete crystal structure at 5 h.With the aging time prolonged,the grains are growing.A large number of precipitates are precipitated at the edge of the grain boundary.At 25 h,the boundary of the cell wall is blurred.The B_r and H_cjj of 2:17SmCo alloy increase first and then decrease with the decrease of aging cooling rate.When the cooling rate is 0.5?/min,the best magnetic energy product?BH?_max=20.98 MGOe is obtained.The content of Sm in 2:17 SmCo alloy is measured by fluorescence spectrometer and the Sm element decreases from 16.93wt%to 16.02 wt%.