Effects Of Ce And La Doping On Magnetic Properties And Microstructure Of MnBi Permanent Magnet Materials

In view of the high price of heavy rare earth elements and supply,it is of great significance to select an excellent low-rare-earth or rare-earth-free permanent magnet material.The rare-earth-free permanent magnet material MnBi has a positive temperature coefficient of coercivity in the temperature range of 150 K-550 K,and shows good application potential among many non-rare-earth permanent magnet materials.However,due to the peritectic reaction and other problems in the MnBi system,it is difficult to prepare high-purity MnBi materials,and the magnetic properties of pure MnBi permanent magnet materials are low.Since the price of Ce and La raw materials has fallen,the price of MnBi raw materials has increased,and it is of practical significance to dope Ce and La elements in MnBi materials.In this paper,under the idea of controlling variables,on the basis of optimizing the magnetic properties of pure MnBi materials,the effects of Ce and La elements on the magnetization behavior,working environment and micro structure of MnBi materials are studied.This article consists of the following parts:1.The effects of rapid melt quenching and tempering on the magnetic properties of MnBi permanent magnet materials are studied.It is found that the tempering temperature is 563 K,and the best performance is that the tempering time is 12 h,and the magnetic properties are the best Mr.The value is 27.65 A·m2·kg-1,and the Hcj value is 341.13 kA·m-1;the linear speed of the copper roll is 30 m/s,the tempering temperature is 563 K,and the duration is 2.0 h.The thin strip has the best performance,Hcj is 423.05 kA·m-l,and the Mr value is 24.75 A·m2·kg-1.The overall performance of the thin strip is better,the process time of the thin strip is much lower than that of the powder,the thin strip is selected as the follow-up experimental research object.2.The effect of La element doping on the magnetic properties of MnBi permanent magnet materials was studied.The DSC results show that an appropriate amount of La element can slightly reduce the difficulty of α-phase formation(2 K-3 K)in MnBi materials;the room temperature(BH)max of the Mn52Bi48 heat-treated ribbon samples is 17.84 kJ/m3,and the room temperature(BH)max of the Mn50Bi48La2 sample is 17.84 kJ/m3.It is a thin strip of 27.06 kJ/m3,which is about 1.5 times that of the tempered thin strip of Mn52Bi48,indicating that an appropriate amount of La element can improve its magnetic properties;It indicates doping with appropriate amount of La improve the purity of α phase.3.The effects of Ce element doping on the magnetic properties and micro structure of MnBi permanent magnet materials are studied.The(BH)max of the Mn50Bi48Ce2 ribbon is 18.23 kJ/m3,which is about 4 times that of the Mn52Bi48 ribbon.The mass fraction of α phase in the Mn50Bi48Ce2 ribbon is 75.60%,which is about 4.27 times that of the Mn52Bi48 ribbon,While purifying MnBi,its magnetic properties are improved;SEM results show that Ce element can greatly increase the contact area between Mn and Bi elements,which is conducive to the formation of phase,TEM results show that Ce element enters the phase lattice,which may lead to magnetic anisotropy The results of the recovery curve show that the exchange coupling of the Mn50Bi48Ce2 ribbon is stronger than that of the Mn52Bi48 ribbon,it’s operating magnetic loss is much lower than the Mn52Bi48 ribbon.