Effects Of LaCe Elements In Different Proportions On The Properties And Microstructure Of Re-Fe-B Magnets

Since the advent of Nd-Fe-B sintered magnets in the 1980s,the related industries have developed rapidly,effectively alleviating the use of strategic resources Sm and Co.Among the naturally distributed rare earth resources,Pr and Nd elements account for approximately 25%,and their associated La and Ce elements account for approximately 72%.The large use of Pr and Nd elements means that the associated La and Ce elements are heavily piled up.The use of La and Ce elements to replace the scarce Pr and Nd elements is not only beneficial for reducing the cost of magnets,but also conserving rare earth resources.In this paper,RE-Fe-B sintered magnets were prepared with La and Ce,and the effect of micro-structure and element distribution on the LaCe coexisting magnetic performances were investigated.RE₂Fe₁₄B sintered magnets were prepared by using LaCe elements instead of Nd elements.The effects of different LaCe contents on the magnetic properties and micro-structure of the magnets were studied.The design substitution amounts were20%,30%,40%,and 50%.The magnetic properties of the magnet rebound when the substitution amount is 30%,and its residual magnetism is 11.96kGs,the coercivity is7.35kOe,and the maximum magnetic energy product is 31.21MGOe.As the substitution amount of LaCe element continues to increase,the magnetic properties maintain a monotonous downward trend,and the phenomenon of agglomeration of rare earth-rich phases in the micro-structure of the magnet increases.Besides,La element shows a strong tendency to enter the main phase in low-substitution magnets.In order to further study the effect of LaCe coexistence on the magnet properties,sintered magnets with four components of LaCe element ratio of 4:1,3:2,2:3 and 1:4 were prepared for each substitution.The results found that changes in the ratio of LaCe elements will cause the magnet performance fluctuation,especially the coercive force,which increased with the LaCe substitution increment.The coercivity difference can reach 0.31kOe,1.15kOe,3.03kOe with 20%,30%,and 40%substitution of LaCe elements,while the residual magnetic difference is only 0.68kGs,0.72kGs,0.74kGs.Among them,the magnet possesses the best comprehensive magnetic properties with the LaCe element ratio of 2:3,which resulted from the inhibition of CeFe₂ phase precipitation caused by La.Besides,the agglomeration of the rare earth-rich phase in the grain boundary is moderated.The total amount of rare earth elements in the main phase of the magnet also reached the peak because of the optimization of the grain boundary layout.The atomic ratio of La element in the main phase is abnormal when the LaCe ratio is 1:4.In this composition,the La element shows a stronger tendency to enter the main phase,which directly causes the Nd element declined in the main phase.Therefore,there is an optimal ratio among the LaCe elements,under which the magnet exhibits the optimal microstructure and magnetic properties under the changed ratio.