| The investigation and development status have been synthetically commented in this paper. The dependence of magnetic property of high coercivity NdFeB magnets on the composition, preparing processes and microstructure has been investigated emphatically. Our work includes two aspects:1. The preparing processes, microstructure and magnetic properties of high coercivity sintered NdFeB magnetsThe advanced processes for preparing sintered magnets with excellent property include the Strip Casting (SC), Hydrogen Decrepitation (HD), Jet Milling (JM) and Rubber Isotropic Press (RIP), whose characteristic and advantages comparing to conditional processes have been introduced. By using the SC, HD and JM processes to prepare the magnetic powder and RIP to compact the blank, suitably adjusting all process parameters, we obtained the high coercivity sintered magnets.The Nd31-xDyxFebalCo2B1(x=1-7wt%) and Nd27Dy4FebalCo2GayB1(y= 0.5,1.0, 1.5,2.0 wt%) sintered magnets with different Dy and Ga content have been prepared by using the advanced processes. The experimental results showed that Co addition can increase the Curie temperature, decrease the temperature coefficient and enhance the temperature stability. The addition of Dy increases the anisotropy of materials, decreases the grain size, prevents the formation of soft a-Fe in the alloys, effectively improves the microstructure, and so obviously enhances the coercivity of magnet However, the addition of Dy decreases saturation polarization, remanence and the energy product of magnet The suitable content of Dy should be 3-4 wt%. The special lubrication of Ga makes the grain boundary more clear and complete, effectively prevents the exchange-coupling interaction between the main phase grains, which lead to enhance the coercivity and decreases the irreversible loses. The nonmagnetic Ga would decrease the remanence and energy product So, the optimum content of Ga should be about 0.5wt%. By Using SC, HD, JM processes, we prepared... |
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