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In order to reduce the Production cost for making Nd-Fe-B magnets, which has record magnetic Properties, a new production technology, reduction-diffusion process, was studied.In which Nd2O3 is used as start ing material to work out Nd-Fe-B permanent magnets directly.The effecte of the contents of Nd, as basic constituent, and Al, Co, as substitute constituents, and some technologic factors on permanent magnetic properties are studied.The practical permanent... In order to reduce the Production cost for making Nd-Fe-B magnets, which has record magnetic Properties, a new production technology, reduction-diffusion process, was studied.In which Nd2O3 is used as start ing material to work out Nd-Fe-B permanent magnets directly.The effecte of the contents of Nd, as basic constituent, and Al, Co, as substitute constituents, and some technologic factors on permanent magnetic properties are studied.The practical permanent magnets of Nd-Fe-B and Nd-Fe-Co-B are made out.The optimum magnetic properties are Br = 13.7T,MHc = 0. 46MA/m, (BH)max= 286.5KJ/m3 The experimental result shows that oxygen is harmful to magnet properties, so it must be controlled below 0.8%. 为了降低具有卓越永磁性的Nd-Fe-B磁体的制造成本,使之更快得到推广使用,本文研究了采用还原—扩散工艺路线,直接用Nd_2O_3作为原材料制取Nd-Fe-B磁体的方法、研究了基本组元Nd和添加元素CO、Al的含量对永磁性能的影响,成功地制造出Nd-Fe-B系永磁体。其中最佳性能为Br=1.30T,_MH_C=0.46MA/m,(BH)_(max)=286.5KJ/m~3。实验结果还表明,氧在合金中起着有害作用,为了获得优异的磁性能,含氧量必须被控制在0.8%以下。 Curie temperature for Nd-Fe-B magnet was determined by DSC set and thermal demagnetization curve, called σ-T curve, was drawn by magnetic balance. High-temperature metallography was used for directly observing the domain variation with temperature.Both melting process of Nd-rich phase and oxidizing process on specimen surface were observed as well.According to the experiments, the Cuire temperature of Nd2Fe14B phase is 307.51℃ (580.5K) and the melting point of... Curie temperature for Nd-Fe-B magnet was determined by DSC set and thermal demagnetization curve, called σ-T curve, was drawn by magnetic balance. High-temperature metallography was used for directly observing the domain variation with temperature.Both melting process of Nd-rich phase and oxidizing process on specimen surface were observed as well.According to the experiments, the Cuire temperature of Nd2Fe14B phase is 307.51℃ (580.5K) and the melting point of Nd-rich phase is approximately 6001. The domain structure in Nd2Fe14B phase is just the same as observed in Co single crystal with strong uniaxial anisotropy. If the domain space becomes wide enough, in order to reduce magnetostatic energy of system, then a certain amount of cone-like reversed domains would appear on the surface rather than transverse closure domains, as in the case of Si-Fe sheet. Magnetic contrast of domain decreases with increasing temperature continuously, but, neither local migration of domain walls nor partial regulation of domains can be found until Curie temperature.During cooling, renucleation of domain in the thermal-demagnetized specimen, which has to fit in with crystal orientation, still shows some randomness; consequently, the domains in same grain before and after thermal demagnetization are almostly identical. The Variation of hardness for the magnet within temperature range of 20-750℃ was studied. 用DSC仪测定了Nd-Fe-B磁体的居里温度,以磁秤法绘制了热退磁曲线(σ-T)。并用高温金相显微镜直接观察了Nd-Fe-B磁体畴结构随温度的变化,对畴结构的特点作了初步讨论。同时观察了富钕相的熔融和试样表面的氧化过程。测定了在20℃到750℃磁体维氏硬度的变化。 The normal composition Nd15Fe77B8 is usually used for producing sintered Nd-Fe-B magnets. The magnets are generally composed of Nd2-Fe14B main phase plus Nd-rich and B-rich minor phases. This paper has emphatically investigated the condition necessary for the existence of the B-rich phase, the structure of the B-rich phase and its influence on magnetic properties. The B-rich phase is a stable NdFe4B4 compound... The normal composition Nd15Fe77B8 is usually used for producing sintered Nd-Fe-B magnets. The magnets are generally composed of Nd2-Fe14B main phase plus Nd-rich and B-rich minor phases. This paper has emphatically investigated the condition necessary for the existence of the B-rich phase, the structure of the B-rich phase and its influence on magnetic properties. The B-rich phase is a stable NdFe4B4 compound and belongs to the tetragonal system with a=7.10A and c=26.47A, having a weak magnetic property. A large number of investigations has shown that the magnetic properties of Nd-Te-B magnets depend directly on its microstructure. Though the influence of the B-rich phase on the coercivity of the magnets is not as essential as the Nd-rich phase, its existence decreaces the saturation magnetization of the magnets. The optimum Theoptimum performance magnets with maximum energy product of 355.8kJ/m3 have been obtained by reducing or eliminating the B-rich phase throughc ontrolling the composition of the alloy. 制造Nd-Fe-B烧结磁体通常采用Nd_(15)Fe_(77)B_8公称合金成分。这种磁体一般由主相Nd_2Fe(14)B和次要富钕相和富硼相组成。本文着重研究了富硼相的存在条件、结构及其对磁性能的影响。富硼相是个NdFe_4B_4稳定的化合物,属于四角晶系,晶格常数α=7.10A,c=26.47A,为弱磁性相。大量研究表明,Nd-Fe-B合金的磁性能直接取决于其相组成。富硼相对磁体矫顽力的影响不象富钕相那样至关重要,但是它的存在会降低磁体的饱和值,我们通过调整合金成分,力图避免或减少富硼相,得到了磁能积为355.8kJ/m~3的最佳性能磁体。
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