Research Of Bonded NdFeB Magnetic Powders Produced By HDDR Process

Since its invention in 1983, rare-earth NdFeB magnets have occupied a huge market in the past two decades ranging from voice coil motor for hard disc drive,magnetic resonance imaging devices to motors for automobile and power generator, because of its high magnetic performance.The growing demands for NdFeB magnets require not only its superior magnetic properties but also additional properties such as corrosion resistance,thermal stability and mechanical properties etc.How to improve properties become a important issue at present.We designed three contents:Nd12.5FebalCo15B6.5Zro.5Gax(X=0,0.25,0.5,0.75); Nd11.5Dy1.0FebalCo15Gao.3B6.5ZrY(Y=0,0.1,0.2,0.3); Nd12.2FebalCo15B6.oGao.5Vz (Z=0,0.1, 0.3,0.5), and We have produced anisotropic bonded NdFeB magnetic powders by using HDDR(hydrogenation,disproportionation,desorption,recombination) process. Based on the aim of high magnetic performance, we studied the influence of different technologies of HDDR (disproportionation time, disproportionation pressure, disproportionation temperature, desorption-recombination temperature) and different contents(add Ga, Zr, V) on the magnetic properties of NdFeB alloy. In this thesis, the XRD Patterns were studied by using X-ray diffraetion. The main results are as follows:1. The X-ray diffraetion results show that, the phases change during the HDDR process. After HD process, the original cast structure Nd2Fe14B phase(about 64.346μm) was firstly decomposed into NdH2,α-(Fe,Co)å'Œ(Fe,Co)2B; and after the HDDR process, the three phases recombination into Nd2Fe14B(about 0.486μm).2.The addition of alloying elements can significantly improve the magnetic properties. The best volumes are as follows:The best additional volume of Ga is 0.5at%, the content of corresponding is Nd12.5FebalCo15B6.5Zr0.5Ga0.5; The best additional volume of Zr is 0.2at%, the content of corresponding is Nd11.5Dy1.0FebalCo15Ga0.3B6.5Zr0.2; The best additional volume of V is 0.3at%, the content of corresponding is Nd12.2FebalCo15B6.0Ga0.5V0.3.3.The adjustment of HDDR procss can improve the magnetic properties. For the three contents, the best technologe we found during the experiment is:room temperature× 0.1MPa×1hâ†'820℃×0.03MPa×2.5-3hâ†'820-830℃×low vacuum×15minâ†'820-830℃×high vacuum×30min。4.The best volumes and the magnetic properties we got: The best volume is Nd12.5FebalCo15B6.5Zr0.5Ga0.5, the best magnetic properties are: (BH)m=159.47kJ/m3, Br=1.10T, jHc=769.51kA/m, DOA=0.55 The best volume is Nd11.5Dy1.0FebalCo15Ga0.3B6.5Zr0.2, the best magnetic properties are: (BH)m=134.96kJ/m3, Br=1.19T, jHc=316.72kA/m, DOA=0.740 The best volume is Nd12.2FebalCo15B6.oGa0.5V03, the best magnetic properties are: (BH)m=104.88kJ/m3, Br=1.15T, jHc=125.73kA/m, DOA=0.609...