橡塑磁体的研究发展现状

本文分别就橡塑磁体的磁粉、粘结剂和配合剂等的研究发展现状作了介绍,并对橡塑磁体需要进一步解决和研究的问题提出了几点看法.     

Dependence of the emission electric dipole line strength of Eu~(3+) on the composition of lead borate glasses

Lead borate glasses xB2O3+(99-x)PbO+0.5Eu2O3(x=70,60,...,10) were prepared by melt-quenching method.The luminescent properties were characterized with excitation and emission spectra.The emission intensities for 5D0-7FJ(J=0-4) were analyzed to give variation of the relative electric dipole line strengths with the composition of glasses so as to examine the crucial implicit assumption of independent electric dipole line strength on the composition of glass in the Phys.Rev.Lett.2003,91,203903 paper studying l...     

粉末粒度对注射粘结磁体性能的影响

实验分析了粉末粒度对制得的注射粘结磁体密度、取向度和磁性能的影响,得出了磁粉粒径太大和太小均不利于磁体磁性能的提高的结论．同时,通过搭配不同比例的粉末,可以提高磁体的装载量,从而达到提高磁性能的目的．     

影响压延取向粘结磁体性能的因素

从分析压延取向对粘结磁体矫顽力等的机制入手,通过扫描电镜、图象仪等工龄研究了影响磁粉形貌及磁体性能的因素,结果表明：磁粉颗粒的径厚比（D／H）是影响磁体性能的关键因素,合适的径厚比能使 粉在取向过程中获得最大有效的取向力矩,同时又能使该应力所引起的晶格畸变最小,获得综合性能优越的磁体;还他磁粉预烧温度、混料方式、预烧助溶剂以及磁体压延取向工艺的混炼温度对磁体性能的影响,为制造磁粉和磁体提供工艺依据。     

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.     

辐射取向环形磁体在磁场中所受磁场力的计算

高均匀性辐射取向环形磁体广泛应用于航空、航天等领域,但其强烈的各向异性的热膨胀性质以及在充磁过程中受到的磁场力均可能导致开裂现象的发生。为了防止辐射取向环形磁体在饱和充磁后因受磁场力的作用而开裂,对磁场力的大小进行了分析和计算。结果表明,辐射取向环形磁体在磁场方向受到一个向外的张力,在充磁过程中,由于圆环的封闭性,这个张力将导致磁体在充磁后裂开;张力F的大小可用公式F=πB2h(R2-R1)/μ进行计算,式中,B为磁感应强度,h为磁环高度,R1和R2分别为磁环内外半径,μ为磁导率。     

磁粉及其偶联处理对压延取向橡胶粘结磁体性能的影响

通过对压延取向橡胶粘结磁体的磁性能及力学性能的测量和在扫描电镜上对磁粉颗粒形貌及粘结磁体拉伸断口形貌的观察研究，表明同样条件下，磁粉径厚比分布合理是保证粘结磁体性能的关键。磁粉大小均匀，径厚比大约在3．0～4．0之间时，磁体综合性能良好；偶联剂的种类及偶联处理工艺也对磁体性能有重要影响。     

Effects of pre-aging on defects evolution and magnetic properties of Sm-Co-Fe-Cu-Zr magnets

The heterogeneous precipitation in the 2:17-type Sm-Co-Fe-Cu-Zr permanent magnets has been found to contain complex formation and dissociation of defects. Though low-temperature pre-aging has been utilized to promote the precipitate nucleation by the enlarged chemical driving force, how the defects evolve after pre-aging and how the possibly changed defects state affects the subsequent precipitation behavior remain unclear. In this work, a model magnet Sm₂₅Co_47.9Fe_18.5Cu_5.6Zr_3.0 (wt%) was selected to study. Through comparison with the as-solution-treated state, it is found that pre-aging for 2 h at 550 °C reduces the defects density, which was characterized by less cell boundaries (i.e., larger cell size) and less basal stacking faults inside the cells (i.e., higher 2:17R ordering degree). Further studies reveal that after aging for the same time (10 h) at the same temperature (830 °C), the reduced density of defects by pre-aging also leads to slower precipitation/phase transformation kinetics when compared with the non-pre-aged one, which was characterized by the lower 2:17R ordering degree and smaller coercivity for the former. These findings suggest that pre-aging has a strong influence on the density of defects and their evolution during subsequent isothermal aging process, which should be carefully considered to tailor the microstructure and magnetic properties of Sm-Co-Fe-Cu-Zr magnets.     

基于ANSYS的铝电解多功能机组小车端梁有限元优化设计

本文采用有限元法对铝电解多功能机组主小车承载结构端梁进行了计算,总结了一种端梁建模和边界条件设置的合理方法,分析了端梁结构的应力和变形分布状态,并提出了结构调整或优化的方案.此外,采用传统力学方法验证了有限元算法的准确性.     

注射成形钕铁硼粘结磁体研究的现状及前景

论述了注射成形钕铁硼粘结磁体的特点及发展趋势,分析了其生产工艺中的4个关键因素,包括磁粉、粘结剂与藕联剂、注射过程、充磁过程,并对这4个关键因素的研究状况作了综合评述,认为今后注射成形钕铁硼粘结磁体的研究开发将主要集中在以下4个方面研究:各向异性粉末和各向异性粘结磁体,研发合适的粘结体系及注射成形工艺参数,开发磁能积更高的磁体,开发耐热钕铁硼粘结磁体。     

注射成形钕铁硼粘结磁体研究的现状及前景

论述了注射成形钕铁硼粘结磁体的特点及发展趋势，分析了其生产工艺中的四个关键因素。包括磁粉，粘结剂与耦联剂，注射过程，充磁过程，并对这四个关键因素的研究状况作了综合评述，认为今后对注射成形钕铁硼粘结磁体的研究开发将集中在四个主要的方面。     

Densification and anticorrosion performances of vacuum evaporated aluminium coatings on NdFeB magnets

Al coated NdFeB magnets obtained by vacuum evaporation technique were densified by high energy ball milling method.The surface morphology,metal composition and micro structure of the coatings were characterized by scanning electron microscopy,X-ray diffraction and X-ray photoelectron spectroscopy,respectively.The anticorrosive properties were investigated by potentiodynamic polarization curves and neutral salt spray test.The pores in the Al coatings of columnar crystals(Al) induced by the evaporation technique,were apparently filled in the following ball milling process,leading to the densification of Al coatings and the evident improvement of the anticorrosive performances.When treated with ball milling for 30 min,the sample achieves the best anticorrosive performances with the self-corrosion potential of-0.87 V,self-corrosion current density of 1.65 μA/cm~2 and the neutral salt spray(NSS) time of 144 h(red rust).The improvement of the anticorro sive performances of vacuum evaporated Al coating mainly lies in the densification effect of the coating,which depends on different loading conditions of ball milling process.     

步进式加热炉生产过程仿真系统设计与实现

步进式加热炉动态生产过程仿真是验证加热炉模型、调整模型精度的有效方法,特别是对于板坯温度跟踪计算,炉温设定方面效果尤为突出.本文介绍加热炉生产过程仿真系统的功能、组成以及没计原理.通过搭建包含板坯装入、移动和抽出等完整功能的仿真环境,为模型研发人员提供一个加热炉模型调试、新模型开发的基础平台.在此仿真平台下,对两种不同出炉目标温度的板坯进行动态仿真,可以发现加热炉模型对不同目标温度的板坯在炉气温度没定上有着明显的区别,从而验证仿真平台是调试模型的有效手段.     

Effects of Pr-Cu-Ti intergranular addition on microstructure and magnetic properties of heavy-rare-earth-free Nd-Fe-B sintered magnets

By intergranular addition of Pr-Cu-Ti alloy powders in the Nd-Fe-B sintered magnets with the normal B component, we propose an approach to the optimization of grain boundary and local Nd-Fe-B composition system. The coercivity is enhanced from 1.42 to 1.86 T, while further addition leads to a reduction in remanence and coercivity. The analyses of phase composition reveal that Ti mainly exists in the form of metallic Ti alloy, and part of Ti combines with B to form the TiB₂ phase after the liquid phase sintering process. This process results in a consumption of B in the local Nd-Fe-B composition system and a change of the grain boundary component, which contributes to the formation process of the RE₆(Fe,M)₁₄ phase after the annealing process. Therefore, with the modification of grain boundary and composition system, the intergranular addition of Pr-Cu-Ti induces the generation of continuous thin grain boundary phases. It promotes the intergrain exchange decoupling, increasing the coercivity in the annealed magnet. While the excess addition results in the segregation of TiB₂, as well as the precipitation of TiB₂ into the Nd-Fe-B phase, which leads to structural defects. Thus, the further effort for the addition alloy with Ti to reduce the deterioration of the microstructure will lead to further improvement in magnetic properties.     

弯桥上简支梁板布设法的探讨

位于路线圆曲线段上的简支梁板桥,预制梁板与公路平面曲线间存在着线形拟合问题,如何布设圆曲线上的简支预制梁板,使其适应路线线形的变化,保证在施工过程中不出现梁板端部抵死无法吊放或落梁,成为一实际工程问题.目前工程上常用方法有平分外矢法、折线布设法、弦线拨角法、加宽桥面法等.然而这些方法在工程上的应用往往是基于实践经验,缺少严格的理论分析.本文正是从理论上应用代数、几何知识推导出以上各种方法的适用范围、应用条件.     

轴承钢端面碎裂原因分析与改进

通过对轴承钢端面碎裂进行分析,认为钢材端部的异常组织是导致矫直后端部碎裂的主要原因。由于轴承钢采用摩擦锯进行定尺锯切,使端部受热,并且端部组织发生了组织转变而产生碎裂。针对分析结果,采取了使用进口锯片锯切的补救措施,解决了钢材矫直过程中的碎裂问题。     

航空正交水平磁偶源频率倾子响应规律研究

随着无人机、卫星导航及微电子技术的发展,航空电磁法勘探成为可能.但是,电磁干扰制约了航空电磁法勘探的发展,为此,提出了航空正交水平磁偶源频率倾子测深法.为了论证该方法的可行性,首先,从有源频率域麦克斯韦方程组出发,利用场的叠加原理,推导了航空正交水平磁偶源水平磁场和垂直磁场的表达式,并构建了张量频率倾子;然后,采用数字...     

石油套管螺纹联接仿真与接箍起始斜度优化

针对API 8牙圆螺纹石油套管接头建立了轴对称有限元分析模型,分析了机紧状态下不同参数接头的典型应力应变及接触行为规律.通过对接箍起始斜度的优化研究发现,接箍最佳起始斜度为50-55°.该结果成功地应用于生产实际.     

Effect of heterogeneous microstructure on magnetization reversal mechanism of hot-deformed Nd-Fe-B magnets

The hot-deformed(HD) Nd-Fe-B magnets show heterogeneous microstructure composed of coarse and fine grain regions. It is significant to fully understand the influence of this complex microstructure on the magnetization reversal process which can give the guidance for the enhancement of the magnetic properties. In this paper, the heterogeneous microstructure of the(HD) Nd-Fe-B magnets were characterized from the morphology, size, macro-texture and micro-structure. In addition, the magnetization reversal process of the HD Nd-Fe-B magnets was systematically analyzed by magnetic measurement, insitu domain evolution observation and micromagnetic simulation. The results indicate that the HD NdFe-B magnets mainly consist of fine grain regions(FGRs) and coarse grain regions(CGRs). The FGRs show plate-like grains with fine grain size and strong c-axis texture, while the CGRs show equiaxial grains with large grain size and weak c-axis texture. In particular, it is worth noting that the texture in homogeneity exists not only between FGRs and CGRs, but also inside both the FGRs and CGRs. The dominant coercivity mechanism of the HD Nd-Fe-B magnets is domain wall pinning. Also, the experimental analysis shows that the reverse domain is formed and expanded in the CGRs at low reverse applied field, while the reverse domain occurs in the FGRs at higher reverse applied field. The micromagnetic simulation results also confirm the above magnetization reversal process. In addition, micromagnetic simulation results also show that the orientation of the grains also affects the pinning strength, besides the grain size.     

Improvement of coercivity and thermal stability of Nd-Fe-B sintered magnets by intergranular addition of Tb80Fe20 alloy

To improve the coercivity and temperature stability of Nd-Fe-B sintered magnets for high-temperature applications, the eutectic Tb₈₀Fe₂₀ (wt%) alloy powders were added into the Nd-Fe-B sintered magnets by intergranular method to enhance the coercivity (H_cj) and thermal stability. The microstructure, magnetic properties and thermal stability of the Nd-Fe-B magnets with different Tb₈₀Fe₂₀ contents were studied. The experimental results demonstrate that the coercivity (H_cj) of the sintered Nd-Fe-B magnet is significantly enhanced from 14.12 to 27.78 kOe, and the remanence (B_r) decreases not obviously by introducing 4 wt% Tb₈₀Fe₂₀ alloy. Meanwhile, the reversible temperature coefficients of coercivity (β) and remanence (α) of the Nd-Fe-B magnets are increased from ?0.5634%/℃ to ?0.4506%/℃ and ?0.1276%/℃ to ?0.1199%/℃ at 20–170 ℃, respectively. The Curie temperature (T_C) of the Nd-Fe-B magnet is slightly enhanced with the increase of Tb₈₀Fe₂₀ content. Moreover, the irreversible flux magnetic loss (h_irr) is obviously reduced as Tb₈₀Fe₂₀ addition increases. Further analysis of the microstructure reveals that a modified microstructure, i.e. clear and continuous RE-rich grain boundary layer, is acquired in the sintered magnets by introducing Tb₈₀Fe₂₀ alloy. The associated mechanisms on improved coercivity and thermal stability were comprehensively researched.