吸氢对HDDR各向异性NdFeB材料的影响

对d HDDR方法制备各向异性Nd1 3FebalB7Co1 1 Zr0 .1 磁粉过程中吸氢处理阶段进行了研究。发现在 933K左右的温度范围内 ,氢压为 0 .1MPa的条件下进行低温吸氢 ,材料发生了剧烈的歧化分解 ,导致材料的各向异性消失 ,这在处理过程中是应避免的 ;而在 373～ 833K温度范围内进行低温吸氢时 ,材料具有优异的磁性能 ,特别是在 473～ 573K时 ,低温吸氢处理过程有明显的细化粉末颗粒的作用。吸氢时间对材料磁性能几乎没有影响。升温过程中保持合适的氢分压既可以避免材料发生剧烈的歧化反应而破坏了磁各向异性 ,又有利于提高材料的矫顽力 ,从而制备具有高性能的各向异性NdFeB材料。当升温过程中的氢压保持在 0 .0 6MPa时 ,最终可以制得矫顽力和各向异性均较好的磁粉 ,其磁体的性能为 :Br=0 .887T ,iHc=885kA·m- 1 ,DOA =0 .61 ,(BH) max=1 2 5kJ·m- 3。     

添加Zr对NdFeB合金HDDR磁粉的磁性能及显微组织的影响

本文主要研究了合金元素 Zr对 Nd Fe B合金 HDDR磁粉的磁各向异性和显微组织结构的影响。研究结果表明 ,Nd Fe Zr B合金磁粉出现了磁各向异性 ,且其显微组织中出现了针状的富 Zr相。     

HDDR钕铁硼材料各向异性产生的机制

研究了NdFeB铸态粉末及HDDR工艺处理过程中不同阶段材料的显微结构、磁性能和各向异性产生的机理.发现NdFeB铸态粉末的各向异性均大于HDDR NdFeB材料的各向异性.随歧化时间延长HDDR NdFeB材料的各向异性单调下降,最终消失,说明HDDR NdFeB材料的各向异性来源于对铸态粉末各向异性的继承;短时间的歧化处理有助于材料获得各向异性;柱状歧化组织作为各向异性的传递介质,以位向关系的方式,将各向异性由铸态粉末传递到了经HDDR处理后的NdFeB粉末.     

HDDR三元NdFeB各向异性材料的制备

研究了HDDR三元NdFeB各向异性磁粉的制备工艺.发现脱氢速度对HDDR三元各向异性NdFeB的磁性能具有显著影响;缓慢的脱氢处理有助于材料获得高的各向异性.在最佳工艺条件下,可获得磁能积为84 kJ·m³的HDDR三元NdFeB各向异性粘结磁体.     

The Effect of HDDR Process on Magnetic Properties in NdFeB Type of Bonded Magnets

The present paper describes the effect of alloy composition,homogenization anddehy-drogenization procedures on magnetic properties of NdFeB type of HDDR powders and the bondedmagnet.The results showed that the powders prepared by HDDR process possesses useful magnetic proper-ties and a better thermal stability than the sintered NdFeB magnet does.     

HDDR各向异性NdFeB磁粉的粒度效应和表面缺陷层模型

研究了HDDR各向异性NdFeB磁粉的粒度效应,发现尽管其粒度效应较低而适合制备粘结磁体,但比快淬NdFeB磁粉的粒度效应显著.在此基础上提出了表面缺陷层模型,即把磁粉颗粒从外表面到内部分成表面缺限层、过渡层和本体部分,磁粉磁性是各自磁性的叠加.     

Cr含量对NdFeB材料微波吸收特性的影响

采用高能球磨和在微氧化气氛晶化热处理的方法制备钕铁硼吸波粉体,借助X射线衍射仪和微波矢量网络分析仪测量系统分析,研究Cr含量对钕铁硼粉体组织结构和微波吸收特性的影响.结果发现:高能球磨和微氧化气氛下进行600℃×2 h晶化处理后Nd11.76 Fes2.35 B5.88粉体组织由α-Fe,Nd2O3,Fe23(B.C)6相组成,加入Cr不改变NdFeB粉体的相组成,但可使粉体中的Fe23 (B.C)6相对量减少,而α-Fe相对量增加;加入Cr可降低NdFeB粉体的复介电常数实部ε’和虚部ε"以及复磁导率实部μ’,尤其是Nd26.67Fe69.83 Cr2.5B粉体的复介电常数虚部ε"降低得最多,加入Cr使NdFeB粉体的复磁导率虚部μ"在4- 10 GHz频段时增大,而大于10 GHz频率后,复磁导率虚部μ"变化不大;吸波涂层厚度为1.5mm时,Nd11.76Fe82.35B5.85粉体的反射率最小值约为-8.5 dB,吸收峰频率约为10 GHz;Nd26.67 Fe69.83Cr2.5B反射率最小值降低到- 17.0 dB,吸收峰频率升高到15.5 GHz,当将Cr含量增加到4％时,粉体的反射率最小值回升到-10.8dB,吸收峰频率升高到15.8GHz;加入Cr会使NdFeB粉体的吸波带宽变窄.     

Effects of Alloying Elements on Microstructure and Magnetic Anisotropy of the HDDR Powder ofNd-Fe-B Alloy

ＥｆｅｃｔｓｏｆＡｌｏｙｉｎｇＥｌｅｍｅｎｔｓｏｎＭｉｃｒｏｓｔｒｕｃｔｕｒｅａｎｄＭａｇｎｅｔｉｃＡｎｉｓｏｔｒｏｐｙｏｆｔｈｅＨＤＤＲＰｏｗｄｅｒｏｆＮｄＦｅＢＡｌｏｙＧａｏＪｉａｎｒｏｎｇ（高建荣），ＳｏｎｇＸｉａｏｐｉｎｇ（宋晓平），Ｗａ...     

Study on Key Techniques for Producing High Performance NdFeB Sintered Permanent Magnets

ＮｄＦｅＢｍａｇｎｅｔｓｈａｖｅｂｅｅｎｉｍｐｒｏｖｅｄｄｒａ ｍａｔｉｃａｌｌｙｓｉｎｃｅｉｔｗａｓｉｎｖｅｎｔｅｄｉｎ 1 983 .Ｔｗｏｔｙｐｅｓｏｆｓｉｎｔｅｒｅｄｍａｇｎｅｔｓ ,ｈｉｇｈｅｎｅｒｇｙｐｒｏｄ ｕｃｔｓ ((ＢＨ ) ｍａｘ)ａｎｄｄｏｕｂｌｅｈｉｇｈ (ｈｉｇｈ(ＢＨ ) ｍａｘａｎｄｈｉｇｈｃｏｅｒｃｉｖｉｔｙ (ｉＨｃ) )ａｒｅｔｈｅｔｗｏｔｅｎｄｅｎｃｉｅｓｆｏｒＮｄＦｅＢｓｉｎｔｅｒｅｄｍａｇｎｅｔｓ .Ｂｏｔｈｆａｃｔｏｒｉｅｓａｎｄｒｅｓｅａｒｃｈｉｎｓｔｉｔｕｔｅｓａｒｅｆｏｃｕｓ…     

Effect of mechanical attrition on microstructure and properties of electro-deposition coatings on NdFeB

Surface mechanical attrition treatment （SMAT） was developed to synthesize nanostructure coatings on alloy surface. The SMAT action was applied in the process of Ni and Cu electroplating coatings on NdFeB substrates in this paper. The role of mechanical attrition during barrel plating on the microstructure, mechanical and corrosion resistant properties of the coatings was exam- ined. The scanning electron microscopy （SEM） observation showed that the mechanical attrition could refine grain size, markedly smooth the coating surface and obviously decrease the number of pore in the coatings. The continuous collisions of glass balls onto the NdFeB samples could induce more beneficial nucleation defects on the coating, which was helpful for increasing nucleation sites and the nucleation rate. The mechanical attrition could also restrain the heterogeneous growth of the coating grain tips due to the abra- sive action of stainless steel balls. The Tafel polarization curve experimental results indicated that SMAT process could enhance the corrosion resistance of coatings on NdFeB. The scratching test revealed that the binding force between coating and NdFeB substrate could be improved dramatically with SMAT process.     

Investigation on the Moldability of HDDR NdFeB Bonded Magnet Prepared by Compression Molding Method

The phenomenon of uneven density distribution is inevitable in the process of preparing bonded magnets with complicated shape or with large geometric size by compression molding due to the friction among magnetic powder grains and between magnetic powder and the die wall, which reduces the pressure along the compression direction. In order to improve the density distribution homogeneity, the thin-wall rings with composition of HDDR NdFeB prepared by compression molding were selected as the investigated object in this study. It was systematically investigated on the effect of addition level of lubricants and the addition methods of lubricants and strengthener on magnet density, density distribution and on magnet strength. By means of joint addition of lubricants and strengthener, which increases the magnet density and improves the magnet density distribution under the precondition of keeping the magnet strength unreduced. Thus the moldability of the bonded magnets is improved.     

Dy对NdFeB永磁合金各向异性的影响

对名义成分为Nd_12.3-xDy_xFe_79.7Nb_0.8Zr_0.8Cu_0.4B₆(x=0,0.5,1.5,2.5)的预合金进行长时间高温退火,将其破碎,取向并粘结.分别沿取向方向和垂直于取向方向测量其磁化曲线.将两曲线延长至相交,交点对应的磁场视为材料的磁晶各向异性场.结果表明:随着Dy含量的增加,合金各向异性场(H_A)呈线性增加.当Dy的原子分数为2.5%时,合金各向异性场达到7536 kA·m^-1;平均每增加1%Dy,各向异性场提高值为200~300 kA·m^-1.     

Multilayer ceramic coating for impeding corrosion of sintered NdFeB magnets

Sintered NdFeB magnets have complex microstructure that makes them susceptible to corrosion in active environments.The current paper evaluated the anticorrosion characteristics of multilayer titanium nitride ceramic coating applied through cathodic arc physical vapour deposition(CAPVD) for protection of sintered NdFeB permanent magnets.The performance of ceramic coating was compared to the electrodeposited nickel coating having a copper interlayer.Electrochemical impedance spectroscopy(EIS) and cyclic polar...     

Influence of Solidification Rate on Microstructures of Cast Strips and Corresponding Sintered NdFeB Magnets

The influences of solidification rate on the microstructures of cast strips and corresponding sintered NdFeB magnets were investigated. The experimental results show that the volume fraction and size of columnar grains vary with the wheel speed V, and the fraction is highest to more than 90% with 3.5 μm in average width at V＝2 m·s-1. The reasons for the improved magnetic performance were discussed based on the micromagnetic theory and microstructure analyses of the strips and sintered magnets. The magnetic properties of sintered NdFeB magnets made from the (Nd,Dy)13.0(Fe,Ga,Al)80.5B6.5 cast strip which was obtained at V=2 m·s-1 are as follows: Br=1.15 T(11.25 kG), iHc=2799 kA·m-1 (35.2 kOe) and (BH)max=242 kJ·m-3(30.35 MGOe).     

注射成型粘结NdFeB永磁体

介绍了粘结永磁体的制备工艺,快淬NdFeB磁粉,HDDR磁粉及粘结磁体的磁性.提出了目前注射制备NdFeB磁体的技术开发要点.     

Preparation Technology and Performances of Zn-Cr Coating on Sintered NdFeB Permanent Magnet

Since appearing in1983,sintered NdFeB perma-nent magnet has been applied widely and become ani mportant basic material in high technology fields be-cause of its excellent magnet property,wide sources ofraw material and low price[1].Active phase such asNd-rich phase and B-rich phase in NdFeB permanentmagnet facilitated easy corrosion in corrosion medium,which weakenedits magnet property,andturnedit intopowder-like,non-usable product.So surface treatingfor anticorrosion was veryi mportant for…     

Model of temperature field for the preparation process of melt-spun NdFeB powders

Melt-spun ribbons which are the important raw material for hot-deformed magnets can be prepared by single-roller melt-spinning. In order to prepare well-structured ribbons, the model of temperature field for single-roller melt-spinning process was constructed in this work. The heat conduction in this process was simplified as one dimensional heat conduction problem. It was shown by modeling that, the temperature field in the melt-spinning before solidification in this model could be described as this equation T(x,t)=Tmoexp[–k(x–x0)–k2αt]+T0. The temperature T(x,t) of the alloy melts decreased with increased position x and cooling time t exponentially from the wheel-free surface to the wheel-side surface. The constant k determined the decrease speed of alloy temperature T(x,t), which was proportional to the interfacial heat transfer coefficient h and the interfacial area of heat conduction A0, but inversely proportional to the thermal conductivity K. x0 was the thickness of the alloy melt. With increased x0, the temperature difference between wheel-free surface and the wheel-side surface became larger, which would lead to larger difference in grain size. In experiments, the influence of melt-spinning process parameters on the temperature field model was discussed, such as cooling roller materials, wheel speed, and so on. Melt-spun ribbons prepared by single-roller melt spinning at different wheel speed were investigated and magnetic properties of die-upset magnets from melt-spun ribbons on different cooling roller were analyzed. The variation of grain size in the depth direction consisted with temperature field model. This model provided directions for the preparation of melt-spun ribbons with uniformly distributed fine grains, which were very necessary for producing hot-deformed magnets with high magnetic performance.     

Characterization of Microstructure and Magnetic Properties of NdFeB Magnet with Dy, Al and Cu Additions

A new alloy of Nd33.5Dy0.99Febal.Al0.52Cu0.1B1.15 (%, mass fraction) was fabricated by powder metallurgy. The effects of Dy, Al and Cu additions on the microstructure and magnetic properties of sintered NdFeB magnet were investigated. The additions of Dy, Al and Cu are effective to refine grains and improve coercivity. Moreover, suitable amounts of Dy, Al and Cu lead to a demagnetization curve with good rectangularity. It is found that the sintered NdFeB magnet has relatively high magnetic performance of Br=12.17kGs, jHc=13.52kOe and (BH)max=34.71MGOe. The sintered NdFeB sample was examined by magnetic force microscope which revealed the domain structures at the surface. It is revealed that the mean Nd2Fe14B grain size is significantly larger than the average scale of the magnetic contrast. An explanation about this is that most Nd2Fe14B grains in sintered NdFeB alloy are dominated with the muhidomain structures when the magnet is in thermally demagnetization state.     

Relationship between controllable preparation and microstructure of NdFeB sintered magnets

The double hard magnetic phase magnets with nominal compositions of Nd_30–xDy_xFe₆₉B₁(x=2, and 4) (wt.%) were prepared. The magnetic properties of the magnets were measured with a NIM-2000H hysteresigraph. The crystalline structures of the magnets were identified by X-ray diffraction (XRD). The Rietveld refinement was carried out using the FULLPROF software. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses were carried out in order to investigate the microstructure of the magnets. It showed that the magnets consisted mainly of Nd₂Fe₁₄B phase, and some Nd-rich phase. Two types of matrix-phase grains in dark grey and light grey were found in the magnets with x=2 and 4. The Dy content was obviously different in the two types of grains, which proved that the double hard magnetic phases (Dy-rich and Dy-lean phases) coexisted in the magnet. It revealed that the Nd-rich phases in junction regions had fcc structure, with the unit cell parameter of about 0.52–0.56 nm. The weak superlattice spots were found in the SAD patterns of the junction Nd-rich phases with large scale. The double hard magnetic phase structure seemed to improve the magnetic properties of NdFeB magnets with high coercivity, while decrease the consumption of Dy element, compared with the single alloy magnet.     

Study on Characteristics of Crystal Growth of NdFeB Cast Alloys

IthasbeenfoundthatthemicrostructuresofcastalloyshavegreatinfluenceonmagneticpropertiesinsinteredNdFeBmagnets .SothecharacteristicsofNdFeBcastalloys ,includingtheshapeofcrystal ,thecompositionanddispersionofphases ,havebeenstud iedbythepeople[1～4 ] .However ,therearefewre portsonthecharacteristicsofcrystalgrowth[5] .Inthispaper ,crystalgrowthorientationofcastalloyspre paredbydifferentprocessingwasinvestigatedusingX raydiffraction ,andtheinfluenceofcoolingrateoncrystalgrowthorientationwasana…