Study On Magnetic Properties And Microstructure Of Hot Deformed REFeB/RECo₅ Composite Magnets

Nanocrystalline composite magnets,a broad prospects for development of new permanent magnet materials,have aroused widespread concern around the world.At present,NdFeB/SmCo₅ composite permanent magnets with high performance and temperature stability have been successfully prepared by hot pressed/hot deformation method at home and abroad.PrFeB/PrCo₅ composite magnets are also prepared by scholars,and because of the same Pr element between the two main phases,the interdiffusion of the two main phases in the preparation process of NdFeB/SmCo₅magnets can be suppressed to a certain extent and the magnetic properties can be improved.According to the recent literature,some scholars obtain a kind of hot deformed NdFeB magnet doped with PrCu liquid phase alloy,the PrCu phase disperses in the interface of the main phases,restrains exchange coupling effect between the main phases and improves the coercivity of the NdFeB magnet.According to previous studies,the content of this paper can be divided into two parts,the first part is the preparation of PrCo₅ magnet undoped and doped with PrCu alloy,and the deformation behavior of the magnet under different deformation condition is observed.The effects of PrCu and deformation condition on the magnetic properties and microstructure of the hot deformed PrCo₅ magnet are studied systematically.The second part is the preparation of PrFeB/PrCo₅ composite magnets undoped and doped with PrCu alloy,and the deformation behavior of the magnets under different deformation condition is observed.The effects of PrCu and deformation condition on the magnetic properties and microstructure of the hot deformed composite magnets are studied systematically.First,in the study of PrCo₅ magnet undoped and doped with PrCu alloy in different deformation condition,the coercivity of PrCo₅ magnet doped with PrCu is higher than that of the PrCo₅ magnet undoped with PrCu under the same deformation condition.The PrCo₅ magnet undoped and doped with PrCu alloy under 70%deformation have the highest coercivity,10.057 kOe and 6.655 kOe,respectively.On the whole,the PrCo₅magnet undoped and doped with PrCu alloy with 70%deformation have the highest magnetic energy product,12.362 MGOe and 11.127 MGOe respectively.The EPMA results show that the Cu element mainly distributes in the interface between the Pr-rich region and the PrCo₅ phase in the 70%hot deformed PrCo₅ magnet doped with PrCu,the PrCu can restrain exchange coupling effect between the main phases and improve coercivity of the hot deformed PrCo₅ magnet.The 70%hot deformed PrCo₅ magnet doped with PrCu is annealed,the PrCu is more uniformly dispersed in the main phases,and the coercivity increased from 10.057 kOe to 14.592 kOe.Second,in the study of PrFeB/PrCo₅ composite magnets undoped and doped with PrCu alloy in different deformation condition,the coercivity of the composite magnets doped with PrCu is higher than that of the composite magnets undoped with PrCu under the same deformation condition.The composite magnets undoped and doped with PrCu alloy under 70%deformation have the highest coercivity,10.760 kOe and 5.596 kOe,respectively.On the whole,the composite magnets undoped and doped with PrCu alloy with 70%deformation have the highest magnetic energy product,13.239 MGOe and9.086 MGOe respectively.A better strips morphology is observed in the SEM results of the70%hot deformed composite magnets doped with PrCu,resulting in a better deformation effect.The temperature coefficient of coercivity of the hot pressed composite magnets is between that of the two single hot pressed magnet.The EPMA results of 70%hot deformed composite magnets doped with PrCu proves that the interdiffusion phenomenon exists between the two main phases.The Cu element is detected in the interface of the two main phases of the 70%hot deformed composite magnets doped with PrCu,and the PrCu can restrain exchange coupling effect between the two main phases and improve coercivity.In the PrCo₅ phase region of the TEM results of the composite magnets parallel to the pressure direction,the grain size is about100nm and the shape is circular,indicating that the deformation texture of PrCo₅ is difficult to obtain.In the PrFeB phase region of the composite magnets,the thickness is about 100 nm and the orientation of the lamellar grains is basically the same,indicating that the deformation texture of PrFeB is good.The TEM results show that PrFeB phase is easily deformed and the PrCo₅ phase is not easily deformed,which affects the deformation effect of composite magnets.