Sm—Fe—N永磁体的研制

用机械合金化的方法及退火和渗氮处理,用纯Fe粉和Sm粉制备出内禀矫顽力为33.1kA/cm(41.6kOe)和磁能积为98.7kJ/m~3(12.4MGOe)的Sm—Fe—N永磁材料.用X射线衍射方法对样品制备过程中的机械合金化、晶化、渗氮过程中所形成的相进行了分析,用脉冲磁强计测量磁性实验结果发现,采用高能球磨机是机械合金化的方法制备高矫顽力永磁体的较好工具晶粒尺度为几十nm是获得高矫顽力Sm—Fe—N永磁体的重要因素,样品中存在的软磁第二相是磁滞回线中出现蜂腰形状的主要原因。     

纳米复合稀土永磁材料

综述了近年来稀土永磁材料发展的一个热点方向－纳米复合稀土永磁材料，分析了硬磁相与软磁相的交换耦合作用；对当前制备纳米复合稀土永磁材料的方法，如机械合金化、 熔体快淬法、磁控溅射法和HDDR法等进行了简单介绍；阐述了纳复合永磁材料的特点和改善其性能的方法。     

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。     

快淬工艺制备钕铁硼纳米复合稀土永磁材料

纳米复合稀土永磁材料具有很高的理论磁性能,因而被认为是最具有发展潜力的新型永磁材料之一。本文以钕铁硼永磁材料为主要对象,介绍了熔体快淬法制备纳米复合永磁材料的工艺方法和研究进展,分析了合金成分、快淬工艺参数等材料微结构与磁性能间的关系,展望了快淬工艺制备纳米复合永磁材料的应用开发前景。     

New permanent magnets and new processing techniques

Since the discovery of Nd₂Fe₁₄B in 1984, a number of new phases with uniaxial anisotropy like Sm(Fe,X)₁₂, Sm₅(Fe,Ti)₁₇, (Sm,Zr)Fe₃, and Sm₂Fe₁₇N₃ have been investigated. Their intrinsic magnetic properties compare favorably with Nd₂Fe₁₄B. Magnetic hardening is possible by rapid quenching or mechanical alloying, which both result in isotropic materials with coercivities of up to 51 kA/cm. Mechanical alloying is a new technique to prepare high- performance permanent magnets at low temperatures. For Nd- Fe- B, isotropic and anisotropic magnets with properties comparable to sintered or melt spun materials can be produced.     

On the use of temperature dependences of the coercive force for an analysis of structural and phase changes that occur upon tempering of alloy carbon steels

The effect of alloying elements Mn, Cr, and Si on the magnetic hysteresis properties of cementite and model steels with a carbon concentration of 0.6 wt % has been studied. It has been shown that alloying with carbide-forming elements (Mn, Cr) reduces the coercive force and the Curie temperature of cementite. Measurements of the temperature dependences of the coercive force of the model steels with carbon content of 0.6 wt % alloyed with manganese, chromium, or silicon have been performed in the temperature range of ?196 to +300°C. It has been established that the local maximum of the coercive force of these steels in this temperature range coincides with the Curie point of the precipitates of the carbide phases. Based on an analysis of the temperature dependences of the coercive force, the content of the alloying element in the precipitates of cementite of steels tempered at different temperatures has been estimated. It has been shown that the character of the dependence of the coercive force of alloy steels on the temperature of tempering in the temperature range of 250–700°C is mainly determined by the coercivity and by the kinetics of the formation of cementite precipitates.     

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…     

粘结剂含量对粘结NdFeB磁体力学性能和磁性能的影响

粘结剂作为粘结NdFeB磁体制备过程中的重要组成部分,其作用是提高磁粉颗粒的流动性和粘结强度,保证产品的力学性能和磁性能的稳定。采用理论与实验相结合的方法,研究了粘结剂含量对粘结NdFeB磁体力学性能和磁性能的影响。在此基础上,制备了高性能粘结NdFeB磁体。利用扫描电子显微镜（SEM）对磁体的结构和形貌进行了表征。在NIM-200C磁滞回线仪和电子万能试验机（AG-X plus）上分别测定了环形粘结NdFeB磁体（RSM）的磁性能和力学性能。结果表明,当粘结剂含量为3%（质量分数）时,粘结NdFeB磁体密度最高（5.59 g/cm³）,抗压强度最高（159 MPa）,磁性能最佳。     

Characterisation of electrochemical interactions between single phases of Nd‐Fe‐B permanent magnets

The electrode functions (anode or cathode) of coupled single phases (ferromagnetic phase: Nd₂Fe₁₄B; boron rich phase: Nd_1+εFe₄B₄; neodymium rich phase: Nd₄Fe) of Nd‐Fe‐B permanent magnets have been investigated. The electrochemical potential differences and current densities between the three phases were determined. Furthermore, the corrosion current density of the magnetic materials in 0.1 M H₂SO₄ was calculated from measurements of current density‐potential curves. The neodymium rich phase works as the anode in contact with both the ferromagnetic and the boron rich phase. The calculation of corrosion current densities for systems of three coupled phases from the current density‐potential curves of single phases measurements demonstrates very high values for the small area of the corroding neodymium rich phase at the grain boundaries. An increase of corrosion resistance of Nd‐Fe‐B‐magnets is possible only by an increase of the corrosion resistance of neodymium rich phase. The presented results do not demonstrate an important influence of the alloying elements gallium or dysprosium on the corrosion rate of the Nd‐Fe‐B magnets. Therefore, new concepts have to be developed to increase the corrosion resistance of these magnets.     

Evaluation of material properties of 3Cr-1Mo-0.25V steel by magnetic, electrical and elastic properties

The magnetic, electrical and elastic properties of 3Cr-1Mo-0.25 V steel were investigated using heat treatment procedures (as-quenched→tempered→PWHT). The mechanical properties were determined for the respective specimens with three types of heat histories. The mechanical properties (yield stress, hardness) and magnetic properties (permeability, coercive force, remanence) were inversely proportional to the heat treatment procedures. The permeability decreased linearly with an increase in the grain size; however, the yield stress, hardness, coercive force and remanence did not vary greatly with grain size. The electrical resistivity and ultrasonic velocity of the as-quenched material differed from those of the tempered/PWHT material. This trend was due to the defects, precipitates and carbides in the grain and at the grain boundary caused by the heat treatment procedures. However, the electrical resistivity and ultrasonic velocity did not vary greatly with grain size.     

Magnetization arrangement of hard magnetic phases and mechanism of magnetization and reversal magnetization of nano-composite magnets

During the process of directional solidification, laser remelting/solidification in the layer on sintered magnets, die-upsetting of cast magnets, or die-upsetting of nano-composites, the arrangements of the easy-magnetization-axes of the hard magnetic phases (Nd₂Fe₁₄B, SmCo₅ or Sm₂Co₁₇ type) in their designed directions have been studied. In Fe-Pt nano-composite magnets, attempts have been taken to promote phase transformation from disordered, soft magnetic A1 to ordered, hard magnetic L1₀ FePt phase at reduced temperatures. The dependence of the magnetization and reversal magnetization processes on the microstructures, involving the morphology and three critical sizes of particles of the FePt nano-composite magnets, are summarized. With the decrease of the nominal thickness of the anisotropic FePt film epitaxially grown on the single crystal MgO (001) substrate, the reversal magnetization process firstly changes from full domain wall displacement to partial magnetic wall pinning related to the morphology change, where the coercive force increases abruptly. The reversal magnetization process secondly changes from magnetic wall pinning to incoherent magnetization rotation associated with the particles being below the first critical size at which multi-domain particles turn into single domain ones, where the coercive force is still increased. And the reversal magnetization mode thirdly changes from incoherent to coherent rotation referred to the second critical size, where the increase of the coercive force keeps on. However, when the particle size decreases to approach the third critical size where the particles turn into the supperparamagnetic state, the coercive force begins to decrease due to the interplay of the size effect and the incomplete ordering induced by the size effect. Meanwhile, due to the size effect, Curie temperature of the ultra-small FePt particles reduces.     

合金元素对烧结NdFeB永磁材料断裂强度的影响

研究了合金元素Ｃｕ,Ｎｂ对烧结ＮｄＦｅＢ永磁材料的抗弯强度和断裂韧性的影响,并采用微观分析方法研究了合金元素Ｃｕ,Ｎｂ对烧结ＮｄＦｅＢ永磁材料的强化机理,结果表明,加入适量的Ｃｕ或Ｎｄ元素能显著提高材料的强度,这主要是因为元素的加入形成了新相,同时还改变了原合金中相的成分。     

放电等离子烧结NdFeB的晶界结构与矫顽力

选取Nd11Dy2Gd2FebalAl4.0Nb0.8Zr0.8B6/Dy2O3磁粉采用放电等离子烧结技术制备各向异性磁体。微观组织和磁性能研究表明,烧结温度对磁体中晶界相的分布形态起决定作用。样品经870 ℃,12 min (40 MPa)放电等离子烧结及后续970 ℃, 2 h + 600 ℃, 1 h二级回火后,致密度达到7.39 g/cm3,剩磁达到1.08 T,矫顽力达到1181 kA·m-1。与同成分的传统烧结磁体相比较,放电等离子烧结磁体中晶界相分布不连续、晶界相中的稀土元素相对含量因烧损而显著下降以及晶界结构存在一定程度的不平衡等问题,都导致磁体的矫顽力较低。     

合金元素对烧结Nd-Fe-B磁体磁性能的影响

述了两类合金元素(代换元素：Co，Dy或Tb与掺杂元素：M1(低熔点元素)：Cu，Al，Ga，Sn，Ge，Zn等与M2(高熔点元素)：Nb，Mo，W，Zr，Ti，V，Cr等)的添加对烧结Nd-Fe-B永磁合金的显微结构和磁性能的影响。综述了两种合金化方式(传统合金化方式：在熔炼前加入合金元素；晶间合金化方式：在球磨或气流磨前加入合金元素)对烧结Nd-Fe-B磁体显微结构和磁性能的不同影响；最后指出晶间合金化复合添加方式是一种很有前景的生产高性能Nd-Fe-B磁体的方法。     

合金元素Co,Zr,Ga在HDDR各向异性NdFeB中的作用

研究了合金元素Co,Zr,Ga对HDDR各向异性NdFeB的磁性能和各向异性的影响,发现Co,Zr,Ga的添加是制备高矫顽力HDDR各向异性NdFeB磁粉的必要因素。研究表明,合金元素Co,Zr,Ga的添加在HDDR各向异性NdFeB制备中的作用主要包括两个方面：首先,合金元素在歧化过程中的富集行为导致了主相Nd2Fe14B在歧化反应中稳定性的提高,从而直接决定了磁各向异性的形成方式;其次,提高了富Nd边界相在氢气中的稳定性,改善了歧化和在复合组织的均匀性。以上两个方面的作用使得材料可以同时具有高的矫顽力和大的磁各向异性。     

铁基纳米软磁合金的制备

介绍机械合金化方法制备纳米软磁合金的试验中,不同的球磨时间与晶粒尺寸之间的变化关系,并分析了晶粒尺寸,镍、钼等元素含量对磁导率、矫顽力、单位质量功耗等软磁性能的影响,认为在铁基纳米软磁合金中适量加入钼有利于改善综合软磁性能。     

放电等离子烧结新型NdFeB永磁材料研究

研究了采用放电等离子烧结技术制备新型NdFeB永磁材料。重点考察了工艺条件对磁体的磁特性、尺寸精度和密度的影响。利用B-H回线仪、扫描电镜和电子能谱对其磁特性、显微组织结构和成分进行了分析测试，同时考察了材料在电解液中的电化学特性及其氧化腐蚀特性。结果表明：与传统烧结NdFeB相比，这种新型NdFeB磁体的显微组织明显不同，其晶粒尺寸细小均匀，富钕相弥散分希；磁体的最佳磁特性为最大磁能积2401kJ／m^3矫顽力1260kA／m；密度达到7．58g／cm^3；尺寸精度为20μm；磁体同时具有良好的抗腐蚀性。     

Corrosion resistance of Nd‐Fe‐B permanent magnetic alloys. Part 1: Role of alloying elements

The electrochemical behaviour of Nd‐Fe‐B magnetic alloys was investigated in acid and neutral solutions. The differences in the chemical composition of these materials have distinct influence on the corrosion rate and polarization behaviour. Small additions of cobalt, aluminium and gallium increase the corrosion resistance of the magnetic alloys at high cathodic potential. It was also observed that the increase of hydrogen evolution rate on the surface of the magnetic materials raises the rate of dissolution of these magnets. The electrostatic surface potential was examined by scanning probe microscopy. A relation between the electrostatic surface potential and electrochemical behaviour of these alloys was found. The high values of electrostatic surface potential of the intergranular phases reflect higher corrosion attack. Auger electron spectroscopy was used to analyse the surface layer which formed during anodic polarization of the magnet containing alloying additives. The result indicates the formation of (Nd,Fe)‐oxide with small amounts of cobalt and aluminium.     

机械合金化W-Ni-Fe纳米复合粉的制备及结构研究

W,Ni,Fe粉末按照91.16W6．56Ni2.26Fe和95W5Ni的成分配比进行了机械合金化(MA)．通过调整球磨转速、球磨时间等工艺参数研究了其对粉末结构的影响,并对机械合金化粉末的物相、合金化特性、晶粒尺寸、点阵畸变及粉末形貌和颗粒度作了测定和分析讨论.机械合金化使晶粒细化并产生孪晶和位错．有利于原子扩散形成过饱和固溶体和非晶；高的球磨能有利于形成非晶相、晶粒细化和点阵畸变，350r／min球磨20h后晶粒尺寸可达25nm；输入的球磨能不同．粉末粒度的变化路径不同，但都会经历长大，变小和稳定三个不同阶段.     

合金元素对单相渗碳体磁性粉体制备及性能的影响

通过机械合金化和真空退火热处理的方法制备了单相渗碳体粉末,并结合第一性原理计算,分析了Mn、Cr和Si对合金渗碳体的成相能力及渗碳体磁学性能的影响.结果表明,机械合金化+600℃真空热处理可获得单相渗碳体.Si的加入完全抑制了渗碳体的生成,而加入Mn、Cr对渗碳体生成有促进作用.Cr、Mn合金化的渗碳体的粉末饱和磁化强...