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Corrosive, brittleness, low temperature sintered NdFeB restricting the further development and application of major defects, studies show that almost all of these defects and grain boundary phase and the grain boundary microstructure closely related, so how to control and optimize the magnet grain boundary structure is the current research hotspot. This article was prepared using powder metallurgy sintered NdFeB magnets by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy spectrum analyzer (EDS), optical microscopy (OM) and other analytical instruments and means systematically studied main element alloy composition Nd, B and Heat Treatment on Sintered NdFeB permanent magnet materials grain boundary composition, grain boundary structure and magnetic properties. Also studied the grain boundary nano ZrC powder grain boundary structure, composition, morphology and magnetic properties. The main findings are as follows: When the Nd content <12.77at%, the Nd-rich phase is too small, less shrinkage during sintering alloy, the density is too low, you can not play a good role to magnetic exchange coupling, resulting magnet H < sub> ci , H k / H ci and (BH) m have declined sharply. When the content of Nd> 12.77 at%, more than Nd 2 Fe 14 B is divided into time-sharing, with the Nd content increases, the volume fraction of the main phase decreased, so that the magnet B r is reduced accordingly, but the Nd-rich phase well undermine the main phase of the magnetic exchange coupling between the grains role in promoting the coercivity increased, while the magnet H k / H ci , (BH) m is relatively high. But the more the grain boundary phase, increasing the content of corrosive anode, increasing the intergranular corrosion, is not conducive to the improvement of corrosion resistance of the magnet. According to the phase diagram shows that, when the B content is less than 5.7%, the alloy appeared Yi base surface Nd 2 Fe 17 phase, when the magnet B r , i H c are relatively low; when the B content is between 5.7 to 5.9 percent, enter T 1 T < sub> 2 Nd phase region, the magnet has a relatively good magnetic properties; when B is added too much, more than 5.9%, the excess B forming a non-magnetic B-rich phase, resulting in the magnet B r dropped, B content is too little or too much, are not conducive to the improvement of corrosion resistance. Magnet components Nd 13.31 Dy 0.48 Fe bal (AlGaNbZr) 0.48 B 5.76 When the corrosion resistance of magnets and magnetic best. Heat treatment can improve the grain boundary phase of the magnet composition, distribution and morphology, the grain boundary phase to promote the precipitation and uniform distribution, thereby increasing the bending strength of the magnet, the magnet 900 ℃, flexural strength at maximum, than the non- handling magnets bending strength increased by nearly 50%. The organizational structure and the magnetic grain boundary phase composition changed, the same will also influence the corrosion resistance of the magnet, the following heat treatment at 600 ℃, with Nd-rich phase increases, the corrosion of the magnet current. As the temperature rises further, to 1000 ℃, the magnet of grain growth, Nd-rich phase reduces network-like distribution, thereby improving the corrosion resistance of the magnet, at 1000 ℃ Nd 13.31 Dy 0.48 Fe bal (AlGaNbZr) 0.48 B 5.76 magnets corrosion current reaches a minimum. Taking into account the magnetic properties of the magnet, for Nd 13.31 Dy 0.48 Fe bal (AlGaNbZr) 0.48 B 5.76 magnet concerned, for 2h 900 ℃ aging treatment can be the most ideal overall performance. ZrC nanopowders can <0.07% added to improve the range of Nd 14.37 Dy 0.4 Fe bal Al 0.98 Nb < sub> 0.14 B 6.57 magnetic coercivity, remanence, maximum energy product and corrosion resistance, when the dosage of 0.03% when the magnet has the best overall performance. The spectrum analysis from the magnet can be seen, the added nano-ZrC powder does not enter the main phase, that is, no change in the intrinsic properties of the magnet, is concentrated in the grain boundary of the Nd-rich rather, changing the electrode potential of the grain boundary phase, etc. Physical and chemical properties, thereby improving the corrosion resistance of the magnet, but considering the magnetic properties of the magnet, the magnet to improve the corrosion resistance of ZrC added only in a certain range. When you add the powder too much time, but will make the magnet performance deteriorated.
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