The Study On The Rare Earth Permanent Magnet Materials Of Nd_8.5Fe_84.5-xNb_0.5Zr_0.5B₆Cu_x（X=0,0.5,1）

NdFeB two-phase composite permanent magnetic materials with exchange coupling are brought to the forefront because of their superior magnetic properties. How to prepare NdFeB two-phase composite permanent magnetic materials which have low rare-earth content and excellent properties is one of the research directions of permanent materials. In this study, by using the rapid quenching of melt method, two-phase composite permanent magnetic materials with three different contents of Cu Nd8.5Fe84.5_xNbo.5Zr0.5B6Cux (x=0,0.5,1) are prepared. Then research on the effects of preparation technological parameter and the addition of element Cu on the microstructures and magnetic properties of NdFeB two-phase composite permanent magnetic materials is conducted by DSC、 XRD and VSM.When with a faster quenching speed of the three kinds of alloy, melt-spun ribbons are mainly composed of amorphous phase and the nucleating particles are reduced in the crystallization process, so much nucleation activation energy need to be overcome for nucleation. Then the nucleation rate is very low and some grains grow abnormally, which go against the promotion of magnetic properties. When with a lower quenching speed, some first crystalline phase contended in melt-spun ribbons like a-Fe and Fe3B, etc. is easy to grow and be coarsened in the crystallization process, which reduces the exchange proportion between soft and hard magnetic phase and influence the magnetic properties of the alloy. When with an appropriate quenching speed of the alloy, some proper crystalline phase in the alloy melt-spun ribbons can be seen as nucleating particle in crystallization annealing, increasing the nucleation rate and blocking the grain growth. Then wee and homogeneous grain structure can be obtained, which improves the comprehensive magnetic properties of the alloy. Alloys with different Cu content have different optimum quenching speed. Nd8.5Fe84.5Nb0.5Zr0.5B6and Nd8.5Fe84Nb0.5Zr0.5B6Cu0.5have optimum magnetic properties at the rapid quenching speed of20m/s, while Nd8.5Fe83.5Nb0.5Zr0.5B6Cu1at 25m/s.This study focuses on the research of the effects of crystallization technology on melt-spun ribbons and magnetic properties. When crystallization temperature too high or crystallization time too long, the crystal particles can fully separate out but the crystal particles will be oversized and the specific surface area will be reduced, which benefits the nucleation of some anti-magnetic domain. Then the exchange coupling between soft and hard magnetic phase is weakened and the magnetic properties of the alloy is reduced. While, when crystallization temperature too low or crystallization time too short, amorphous phase crystallization of alloy is incomplete and the soft and hard magnetic phase separate out less. The existence of amorphous phase blocks the exchange coupling between soft and hard magnetic phase, which influences the improvement of alloy magnetic properties. For alloys with different Cu content, the crystallization technology parameters of optimum magnetic properties are different. For Nd8.5Fe84.5Nb0.5Zr0.5B6, the optimum magnetic property is realized8min after crystallization annealing at750℃and the maximum magnetic energy product is (BH)m=137.21kJ/m3. The optimum magnetic property of Nd8.5Fe84Nb0.5Zr0.5B6Cu0.5is realized20min after crystallization annealing at730℃and the maximum magnetic energy product is (BH)m=103.72kJ/m3. The optimum magnetic property of Nd8.5Fe83.5Nb0.5Zr0.5B6Cu1is realized15min after crystallization annealing at730℃and the maximum magnetic energy product is(BH)m=93.71kJ/m3.Besides, this study also discusses the effects of addition of element Cu on alloy magnetic properties. The research result shows that the addition of element Cu goes against the improvement of alloy’s comprehensive magnetic property. The addition of Cu can accelerate the nucleation of a-Fe phase, but the first precipitated phase is easy to grow and be coarsened in the crystallization process, meanwhile, it goes against the precipitation of hard magnetic phase and Cu is easy to gather between the soft and hard magnetic phase, blocking the exchange coupling and reducing alloy’s magnetic properties.