Study On The Structure And Properties Of NdFeB Based Magnets With High Abundance Of Rare Earth

Since Nd-Fe-B permanent magnet material have been developed since the 1980s,it is one of the foundations of the information industry and has exerted an extremely important influence on the development of modern society.However,the development of Nd-Fe-B permanent magnet material was limited to its poor thermal stability.Although the use of rare heavy rare earth elements such as Tb and Dy can improve the magnetic properties of Nd-Fe-B permanent magnetic materials,but the production cost will also be greatly increased.Therefore,rare earth elements such as La,Ce in a certain range to replace the amount of Nd in the Re-Nd-Fe-B（Re=La,Ce）permanent magnet materials can not only prepare process for low-cost rare earth permanent magnet material foundation,but also better balance rare earth resources and reduce the irrational use of resources.However,the results are not satisfactory.This is due to the lack of research on the composition structure and thermal stability of Re-Nd-Fe-B（Re=La,Ce）permanent magnet materials,which leads to the failure of accurate and efficient alloy design.Therefore,this work mainly focuses on the composition structure,thermal stability and structure-activity relationship of Re-Nd-Fe-B（Re=La,Ce）permanent magnet materials.This work has great significance for the balance of rare earth resources and the exploration of new permanent magnet materials.The research contents of this work can be divided into the following parts:（1）The atomic mobility parameters of the liquid phase and fcc phase of Nd-Fe-B alloy system were obtained by calculation and evaluation.The diffusion database of the alloy system was constructed,and the relationship diagram between solidification path and cooling rate of Nd₂Fe₁₄B alloy was established.The optimal solidification rate of the alloy predicted by the relation diagram was analyzed and verified by experiments.The results show that the simulation results are consistent with the experimental results.In addition,the mechanism of grain refinement of Nd₂Fe₁₄B alloy was studied as well.（2）The structures and thermal stabilities and formation/decomposition reactions of La₂Fe₁₄B have been studied.The double main phase La-Nd-Fe-B permanent magnet material alloy design.The results show that the Nd-La-Fe-B two-main phase permanent magnet with high abundance of rare earth La doped properly still possesses good comprehensive magnetic properties.（3）The structure-activity relationship of Cu doping on the composition,distribution,microstructure and magnetic properties of grain boundary phase of Nd-Ce-Fe-B double main phase magnets was studied.The relationship between magnetic properties and Cu doping amount was obtained.The results shows that the magnetic properties of Nd-Ce-Fe-B double main phase permanent magnets can be improved by Cu doping.In addition,the mechanism of Cu doping to improve the magnetic properties of Nd-Ce-Fe-B double main phase permanent magnets has also been studied.