烧结NdFeB磁体的显微组织与磁性能

纯三元NdFeB磁体的显微组织主要由Nd_2Fe_(14)B硬磁ψ相,富硼Nd_(1+ε)Fe_4B_4η相,富Nd相及少量杂相组成。其中占磁体体积百分比85%～90%的ψ相是非内禀磁特性的主要贡献者;占磁体体积5%的η相对iHc无益,但少许η相仍有利于ψ相形成,富Nd相对ψ相具包裹作用,有助于提高矫顽力;杂相使反磁化畴易于形成,应尽量少。同时,讨论了各显微组织的形成及作用机理。     

富钕相对烧结NdFeB磁体耐腐蚀性的影响

研究了Nd2Fe14B单晶、传统烧结NdFeB磁体和放电等离子烧结（简称SPS）NdFeB磁体在电解液溶液中的电化学特性。采用扫描电子显微镜和电子能谱分析了磁体的微观组织成分。结果表明在3．5％NaCI溶液的极化曲线中，Nd2Fe14B单晶具有最高的电化学腐蚀电位，放电等离子烧结NdFeB磁体的腐蚀电位高于传统烧结NdFeB磁体。与传统烧结NdFeB磁体相比，放电等离子烧结NdFeB磁体富Nd相具有独特的分布形态，主相Nd2Fe14B晶粒细小、均匀，富钕相在主相晶粒边界上分布较少，主要集中在三角晶界处。这种组织结构有效地抑制了磁体沿富钕相发生晶间腐蚀的过程，磁体因此具有良好的耐腐蚀性能。此外，从不同稀土含量的烧结NdFeB磁体的高压加速实验中可以看出磁体的腐蚀速度随稀土含量的增加而增大。以上结果表明富Nd相的化学特性及其分布状态和含量是决定合金耐蚀性能的关键，它在合金中以网络状分布在主相晶粒边界上，并决定了烧结NdFeB易于发生选择性晶间腐蚀，从而导致耐蚀性差。     

烧结NdFeB磁体相的继承性研究

设计成分为Nd32.5B1.04Febal(质量分数,%),经过熔炼,制粉,成型,烧结后制备了烧结NdFeB磁体,对样品的铸锭,烧结态样品以及高温回火态样品,低温回火态样品的微观组织采用SEM进行了仔细地分析。结果显示,烧结NdFeB磁体的相具有"继承性",在熔炼中产生的α-Fe相会被烧结回火后的磁体继承下去,而烧结中形成的Nd2Fe14B相和B-rich相在回火后数量和形态基本上变化不大,Nd-rich相虽然数量变化也不大,但是在高温回火中熔化流动,均匀分布在主相Nd2Fe14B周围,把主相Nd2Fe14B一个个分隔开来,在低温回火中,这种流动会延续,相的形态会得到巩固,使得磁体最终获得良好的综合磁性能。     

WC对Nd—Fe—B烧结磁体的显微组织和磁性能的影响

本文主要研究了在Ｎｄ－Ｆｅ－Ｂ烧结磁体晶界上添加ＷＣ对显微组织和磁性能的影响。实验结果表明，添加少量ＷＣ时，随ＷＣ含量的增加，晶粒逐渐变细，矫顽力也逐渐升高，并且在０．６％处晶粒最细，而矫顽力则出现峰值，进一步增加ＷＣ的含量，晶粒又开始粗化，并伴随着矫顽力的下降。     

烧结NdFeB磁体中相的形态与分布

用扫描电镜（SEM）和电子能谱分析（EDAX）研究了烧结NdFeB磁体中的相的形态和分布。大量研究发现，烧结NdFeB中存在富钕相的偏聚、细小晶粒的“抱团”、晶问和晶内孔隙，一方面使得磁体的致密度下降，另一方面也降低了组织的均匀性，从而使磁性能比较差。     

添加Dy2O3对烧结NdFeB磁体微观结构的影响

研究了NdFeB粉末中添加1wt％Dy2O3粉末对烧结NdFeB磁体微观结构的影响，研究发现，在烧结过程中，Dy2O3中的Dy与Nd2Fe14B中的Nd发生了置换反应，Dy进入Nd2Fe14B相，形成了（Nd，Dy）2Fe14B相，提高了磁体的矫顽力。     

热处理对烧结NdFeB磁体微观结构和磁性能的影响

系统研究了热处理对烧结NdFeB磁体微观结构和磁性能的影响.结果表明：二级回火热处理后,磁体微观组织结构得到明显改善,晶界变得更加规整、平滑,富Nd相均匀弥散地分布于晶粒周围,晶界相成分趋于稳定、均匀;磁体的内禀矫顽力显著提高,剩磁及最大磁能积也有一定程度的提高,极大地改善了磁体的热稳定性.     

添加W,Mo或Nb对Nd—Fe—B烧结磁体显微组织与磁性能的影响

研究了在ＮｄＦｅＢ磁体晶间添加Ｗ,Ｍｏ或Ｎｂ等合金元素对显微组织和磁性能的影响。结果表明,适量的Ｗ,Ｍｏ或Ｎｂ能不同程度提高ＮｄＦｅＢ磁体的矫顽力,对剩磁影响不大。显微组织分析表明,矫顽力的提高可归因于晶间ＴＦｅＢ（Ｔ＝Ｗ,Ｍｏ或Ｎｂ）新相的出现。进一步分析表明,晶间微合金化能够有效改善ＮｄＦｅＢ磁体组织与性能。     

影响烧结NdFeB磁性能因素的研究

研究了烧结NdFeB磁体中富钕相形态、主相晶粒度和初始粉末颗粒的形态等因素对磁性能的影响.结果表明,只有当富钕相均匀分布.且与主相晶粒边界形状相适应时才能起到提高NdFeB烧结磁体磁性能的作用.介绍了取向度的计算以及对磁性能的影响.指出只采用(105)与(006)衍射峰的比值确定NdFeB的取向度不合理,想要获得更精确的取向度应该考虑更多的错取向峰.     

NdFeB纳米复合磁体的微观结构和磁畴结构显微分析

NdFeB纳米复合磁体中硬磁相的某些晶面间距与软磁相的几乎相等，因而采用常规透射电镜进行电子衍射或高分辩像直接鉴定物相相当困难。日本学者采用能谱(EDS)和电子能量损失谱(EELS)鉴定物相和测定了晶粒尺寸分布，并用洛伦兹力显微术研究了磁畴结分 析·检 测 构。样品采用熔体快淬法得到非晶后于973K退火结晶制得。其名义成份为Nd4.5Fe77B18.5，磁能积77KJ/m3，剩磁1.11T。用EELS研究了在997K温度退火的样品。衍衬像和EELS在加速电压为300kV配备有热场发射枪的JEM-3000F型TEM上完成。EDS在加速电压为200KV的JEM2010TEM上…     

回火处理对烧结钕铁硼永磁材料组织和磁性能的影响

探讨了回火处理对烧结Nd-Fe-B系合金显微组织和磁性能的影响.研究表明回火处理后,磁体的显微组织得到明显的改善,主相体积分数增加,晶界变得清晰,晶粒尺寸趋向均匀;颗粒状富Nd相减少,富Nd相沿晶界均匀分布,成分趋于共晶富Nd相的成分;磁体的剩磁、矫顽力和最大磁能积都得到提高,最大磁能积普遍提高20～30 kJ/m3.     

Magnetic force microscope study on anisotropic NdFeB permanent magnets

1　INTRODUCTIONMagneticforcemicroscopy (MFM )hasbeenap pliedtostudythemicro magneticstructureofmag netsformorethanonedecade .Althoughthedevelop mentofMFMtechniqueenablesittoinvestigatethemagneticstructureofvariousmagnets ,especiallyforthosemoderatecoercivitysystemssuchasmagneticsensormaterialsandinformationstoragemedia[1] ,theobservationonthehigh performancepermanentmagnetNdFeBisstillahardnuttocrack .However ,MFMobservationonNdFeBisreallyworthyofre searcheffortsbecauseoftheverystrong…     

Corrosion protection of sintered NdFeB magnets by CAPVD Ti2N coating

Sintered NdFeB magnets have poor corrosion resistance and are readily susceptible to corrosion under different environmental conditions. Cathodic arc physical vapour deposited (CAPVD) titanium nitride coating for sintered NdFeB permanent magnets has been investigated in this paper. Tafel extrapolation was employed to study the corrosion behaviour in 3.5% NaCl solution at ambient temperature. The adhesive strength of the coating was estimated with the help of the scratch test. The surface chemistry and coating morphologies were studied with scanning electron microscope (SEM). X-Ray diffraction (XRD) was used for qualitative phase analyses of coatings and substrate. The properties of CAPVD titanium nitride coating were compared with electrodeposited multilayer nickel–copper–nickel coating. It was figured out that the CAPVD titanium nitride coating had better adhesion strength and shifted the free corrosion potential (FCP) of the system towards positive potential, providing protection to the NdFeB substrate. However, the corrosion rate of CAPVD titanium nitride coating was more than the electrodeposited multilayer nickel–copper–nickel coating. The magnetic properties remained comparable.     

烧结钕铁硼基底成分对晶界扩散效果的影响研究

晶界扩散作为一种能明显提升烧结钕铁硼磁体矫顽力同时实现对重稀土高质化利用的方法,日益成为目前稀土永磁学界和产业界的研究热点。本文利用自动化喷涂设备系统研究了晶界扩散烧结磁体批量制备过程中基底成分差异晶界扩散后磁体磁性能的影响,微观结构和EDS元素分析结果表明：晶界扩散后磁体矫顽力增长幅度的差异,同扩散后磁体内晶粒核壳结构形成充分与否、晶界相均匀分布与否和晶界相铁磁性元素含量高低有密切关联,同时利用晶界扩散工艺制备得到的磁体温度系数要优于传统工艺制备得到的相近似牌号的磁体。     

Effect of Al and Al/Mo addition on microstructure and magnetic properties of sintered Nd22Fe71B7 magnets

1　ＩＮＴＲＯＤＵＣＴＩＯＮＩｔｉｓｗｅｌｌｋｎｏｗｎｔｈａｔｔｈｅｉｎｔｅｒｇｒａｎｕｌａｒｍｉ ｃｒｏｓｔｒｕｃｔｕｒｅｏｆｓｉｎｔｅｒｅｄＮｄ Ｆｅ Ｂｍａｇｎｅｔｓｐｌａｙｓａｋｅｙｒｏｌｅｉｎｄｅｖｅｌｏｐｉｎｇｔｈｅｉｒｃｏｅｒｃｉｖｉｔｙ[1,2 ].Ｅａｒｌｉｅｒｓｔｕｄｉｅｓｓｈｏｗｅｄｔｈａｔｔｈｅｉｎｔｅｒｇｒａｎｕｌａｒｍｉｃｒｏｓｔｒｕｃｔｕｒｅｉｓｃｏｍ ｐｏｓｅｄｏｆａＮｄ ｒｉｃｈｐｈａｓｅａｎｄａｓｍａｌｌａｍｏｕｎｔｏｆＢ ｒｉｃｈｐｈａｓｅ[3].Ｉｔｈａｓｂｅｅｎｓｈｏｗｎ…     

温压工艺对粘结NdFeB磁体性能的影响

采用温压工艺制备粘结NdFeB磁体,发现温压技术可以有效地提高牯结磁体的密度.改善磁体磁性能.研究表明:温压效果与温压温度的选择和温压压力密切相关.通过对温压机理的分析,发现最佳温压温度由粘结剂的软化点、粘度和固化点三个因素共同决定.而随着温压压力的升高,粘结NdFeB磁体的密度和磁件能增大,并在压力为650 MPa时得到了粘结磁体磁能积的最大值(50.43 kJ/m~3).     

Preparation and characterization of TiO_2/acrylic resin composite coatings on sintered NdFeB permanent magnets by electrochemical deposition

The sintered Nd Fe B permanent magnets are widely used in various industries because of their excellent magnetic and comprehensive properties. However, they are seriously hindered to further developments and applications owing to its poor corrosion resistance. In this paper,TiO2/acrylic resin composite coatings were successfully prepared on the sintered Nd Fe B permanent magnets by electrochemical deposition for the first time, and the corrosion behaviors were investigated by using immersion testing and potentiodynamic polarization tests. It is found that the coating is a composite, being composed of polymerized acrylic resin as the matrix and nano-rutile TiO2particles(-200 nm) as the reinforcements. It is about25 lm in thickness and its surface and cross-section exhibit uniform and smooth with no pores, cracks, and other defects. Compared with those of the uncoated Nd Fe B magnets, the weight loss of the coated samples immersed in H2SO4 solution reduces by two orders of magnitude,corrosion current density decreases by four orders of magnitude, and the corrosion potential of the coated sample is shifted in the noble direction by 400 m V. The mechanisms of corrosive resistance enhancement were discussed.     

优化边界结构改善烧结Nd-Fe-B永磁材料的力学性能

在富稀土辅合金中添加Co,Nb,Ti,Ga,Al等元素,用双合金工艺制备一系列不同辅合金含量的烧结Nd-Fe-B磁体,对力学性能进行系统研究。结果表明,在主合金(NdDyTb)12.69(FeCoNb)84.01B6.00的基础上添加3.0wt%的(NdDyTb)25(FeCoNbTiGaAl)68B7富稀土辅合金,其抗弯强度从316MPa提高到344MPa,抗弯强度的改善来自于边界结构的改善以及一些新相的生成。当辅合金含量达到8wt%,合金的强度又下降为321MPa。还研究了热处理工艺对Nd-Fe-B永磁材料力学性能的影响,含3.0wt%辅合金的磁体抗弯强度由烧结态的291MPa提高到最佳回火态的344MPa,又下降为非最佳回火态的304MPa。     

Influence of dynamic crystallization on exchange-coupled NdFeB nanocrystalline permanent magnets

Dynamic crystallization was introduced to improve the magnetic properties of NdFeB nanocrystalline permanent magnets by optimizing microstructure. The microstructure was studied by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It has been determined that, compared with the conventional heat treatment, dynamic crystallization can shorten the crystallization time. Moreover, dynamic crystallization can refine grains, enhance the exchange-coupled interaction among grains, and promote the magnetic properties. As a result, the optimal magnetic properties of Nd10.5(FeCoZr)83.4B6.1(Br＝0.685T, Hci ＝732 kA·m -1 , Hcb ＝429 kA·m-1 ,( BH )m=75 kJ·m -3 ) are obtained after dynamic crystallization heat treatment at 700 ℃ for 10 min.     

烧结钕铁硼添加合金元素的研究进展

磁性能优越的烧结钕铁硼永磁材料已成为永磁产业的支柱.过去的二十多年里钕铁硼已经在硬盘驱动器的VCM、电动机、信号发生器、手机和MRI等多种器件中得到广泛应用.在未来,由于汽车和电子应用领域对节能电动机的需求,使得电动机市场有望进一步扩展.因此,研究团队致力于钕铁硼磁性能的提高,从而推进电动机市场的快速发展.本文对近些年...