Study On Preparation And Properties Of Rapid Quenching Ndfeb Rare Earth Permanent Magnet Powder

Because of its excellent magnetic properties, NdFeB permanent magnets have been widely used in many fields such as computer, car, audiovisual,et al. In this essay, NdFeB rare-earth permanent powder was prepared by melt-quenching method in an effort to improve the magnetic properties of NdFeB rare-earth permanent powder. The effects of quenching velocity, annealing temperature, annealing time and alloy compositions on NdFeB rare-earth permanent powder micro-structure and magnetic properties were explored systematically. The main results are as following.The quenching velocity plays an important role in NdFeB rare-earth permanent powder micro-structure and magnetic properties. The magnetic performances of NdFeB rare-earth permanent powder become bad at too high or too low quenching velocity. At lower annealing temperature and short time, NdFeB rare-earth permanent powder can not be completely crystallized which results in lower magnetic properties. However, at higher annealing temperature and time, the grain sizes of NdFeB rare-earth permanent powder is too larger which can also resulting in lower magnetic properties.The results of the effects of alloy compositions show that the diffraction peak ofα-Fe phase becomes weak with the increase of Nd content at a range of 9at%～12at%. The remanence, coercivity and maximal magnetic energy product increase with the increase of Nd content, and then maximal magnetic energy product reaches its maximum at Nd content of 10.5at%. However, with the farther increase of Nd content, the magnetic properties of the samples decrease gradually. With the increase of B content, the properties of the samples increase and reach to a maximum at B content of 6.2at%, then decrease with farther increase B content. The content of Co has no obvious affects on the magnetic performances of NdFeB rare-earth permanent powder. The addition of Zr can restrain the growth of grain size of the samples which can result in small grain size. And the addition of Zr can also improve the coercivity of samples by pinning the movement of magnetic domain wall. Moreover, the layer by layer structure of alloy ingot presents at condition of the addition of Zr which is favor to the crash of alloy ingots. However, the remanence of the samples decreases with the addition of non-magnetic element Zr.The optimized preparing parameters are 22m/s of quenching velocity,700℃of annealing temperature and 15min of annealing time. The optimized alloy compositions are Nd10.5Fe75.3Co6Zr2B6.2 and Nd10.5(FeZr)83.3B6.2. The optimized magnetic properties of magnetic powders are 0.889T of Br,1020kA/m of Hcj,107.9kJ/m3 of (BH)max.