Structural Evolution And Magnetic Properties Of Ce-Nd-Fe-B Based Nanocrystalline Magnets

With the increase of Nd-Fe-B production,the consumption of rare earth Nd/Pr/Dy/Tb resources is also increasing rapidly.The La,Ce and Y rare earths,as accompanying products,have been oversupplied and piled up in large quantities for a long time,which has seriously affected the balanced utilization of rare earth resources.Therefore,it is imperative to expand the application of high-abundance rare earth La,Ce and Y in Nd-Fe-B magnets.Which is in order to achieve production cost control,promote the balance between production and sales of rare earth products,relieve environmental pollution pressure,promote the efficient and balanced utilization of rare earth resources.In this paper,Ce-Nd-Fe-B based nanocrystalline magnets were prepared by using the Spark plasma sintering and the dual-alloy method.The evolution of magnetic properties,microstructure and intercrystalline magnetic interaction of the magnets were discussed,and the relationship between the metallurgical behavior of elements,phase structure and temperature stability was explained.Firstly,through the composition design and melt quenching technology,the nanocrystalline(Y,Ce)-Nd-Fe-B alloy ribbons was prepared.The magnetic properties,phase composition,thermal stability and microstructure of(Y,Ce)-Nd-Fe-B alloys with different Nd contents have been systematically studied,and the magnetic interactions between the alloys have been analyzed.The results show that with the increase of Nd content,the Ce Fe₂ phase in(Y,Ce)-Nd-Fe-B alloy tends to disappear,which is conducive to the increase of magnetic properties.Among them,the magnetic properties of(Y₅₀Ce₅₀)₁₀Nd₂₀Fe_68.9B_1.19 alloy increase most obviously,and their magnetic properties are:H_cj=1042 k A/m,J_r=0.74 T,(BH)_max=91k J/m³.The results show that all the samples show strong exchange coupling and the effect of remanence enhancement is significant.Secondly,the(Y,Ce)-Nd-Fe-B nanocrystalline magnet was prepared by using the optimized alloy as raw material.The results show that different sintering temperature has a great influence on the magnetic properties of the magnet.With the increase of temperature,the magnetic properties of the magnet show a downward trend,and the square degree of the magnet deteriorates.When the sintering process is 650 ?/50 MPa/5 min,the magnetic properties of SPS-20 magnet is as follows:H_cj=725 k A/m,J_r=0.73 T,(BH)_max=81 k J/m³.The microstructure analysis shows that in the sintering process,the magnet forms two kinds of areas:coarse grain area and fine grain area.And the sintering temperature has a great influence on the coarse grain area.The higher the sintering temperature,the more obvious the abnormal grain growth,and the more significant the deterioration of magnetic properties of the magnet.The study of element distribution in magnets shows that Nd and Ce are abundant in grain boundaries,Y is evenly distributed in magnets and tends to enter 2:14:1 main phase,which is beneficial to the stability of the main phase.Finally,due to the lack of intrinsic magnetic properties of Ce-Fe-B and the excellent intrinsic magnetic properties of Pr-Fe-B,Ce-Pr-Nd-Fe-B alloy powders were mixed with Pr-Fe-B alloy powders.Ce-Pr-Nd-Fe-B/Pr-Fe-B nanocrystalline magnets were prepared,and the magnetic properties and thermal stability of the double alloy magnets were greatly improved.The results show that the magnetic properties of SPS-75 magnet are:J_r=0.80 T,H_cj=865 k A/m,(BH)_max=104 k J/m³,when thecontent of Pr-Fe-B alloy is 75 wt.%.Compared with the magnet that without Pr-Fe-B alloy,the Curie temperature of the magnet increases from 542 K to 563 K after adding Pr-Fe-B alloy,which effectively improves the Curie temperature of the magnet.In addition,by adding Pre-Fe-B alloy can enhance the exchange coupling between grains and weaken the magnetostatic interaction,which is beneficial to the increase of magnetic remanence.In summary,this paper systematically analyzes the magnetic properties and thermal stability of the high-abundance rare earth element Y/Ce containing magnet,including the magnetic microstructure,elements of metallurgical behavior,intercrystalline magnetic interaction.This work provides experimental guidance and theoretical analysis for the preparation of cost-effective rare earth permanent magnet materials.