铽纳米颗粒掺杂烧结高性能NdFeB永磁的研究

分别采用物理气相沉积和快淬-氢爆工艺制备了Tb纳米粉和主相Nd_2Fe_(14)B磁性粉末, 研究了Tb纳米颗粒掺杂对烧结NdFeB永磁磁性能和微观结构的影响. 结果表明, 随着纳米Tb粉含量的增加, 磁体的矫顽力逐渐升高, 剩磁和磁能积则呈下降趋势. 显微组织研究表明, Tb元素富集在主相晶粒的边界层位置, 这种分布方式不仅有效地提高了磁体的矫顽力, 而且降低了Tb的添加量, 从而减小了Tb的添加对磁体剩磁及磁能积的负面影响.     

NdFeB稀土永磁材料的研究现状

NdFeB稀土永磁材料由于具有优异的磁性能而受到人们的广泛关注.系统地介绍了Nd-FeB的微观结构、矫顽力机制、腐蚀机理及其防护、高性能磁体的制备新工艺等,提出了今后的研究和发展方向.     

真空处理对Mo-0．1Zr-0．55Ti合金性能和断口组织的影响

采用粉末冶金方法制备出纯Mo、Mo-0.55Ti和Mo-0.1Zr-0.55Ti合金,研究了真空处理对3种合金性能和显微组织的影响.结果表明,未经真空处理时,纯Mo、Mo-0.55Ti和Mo-0.1Zr-0.55Ti合金发生了明显的沿晶脆性断裂.真空处理对纯Mo和Mo-0.55Ti合金的性能影响不大,合金断口仍然表现为沿晶脆性断裂,但真空处理使M0-0.1Zr-0.55Ti合金的性能,尤其是合金的延性得到明显提高,其延伸率由5.3%提高到12.8%,断口呈现了明显的穿晶断裂特征.     

富镧稀土-Ni对铜合金性能影响的研究

研究了富镧稀土-Ni合金粉在铜合金中的作用，结果表明铜合金中添加适量的富镧稀土-Ni合金粉。硬度、抗弯强度等有很大提高。当富镧稀土-Ni合金粉含量达到1．5％时。硬度达到最高值92．0HRB；富镧稀土-Ni合金粉含量为1．0％时，材料孔隙率达到最低值0．79％，抗弯强度达到最大值640．56MPa。     

放电等离子烧结细晶2024铝合金的腐蚀行为研究

采用放电等离子烧结的方法以5μm和10μm的粉末为原料制备2024铝合金.显微结构分析表明合金中夹杂相分布在晶粒和晶界上,晶界内部夹杂相小于晶界处,SPS-5中的夹杂相比SPS-10中的大.电子背散射衍射表明合金SPS-5的晶粒尺寸(3.92μm)及其分布区间要大于合金SP-10(3.78μm),而电化学测试表明合金S...     

烧结NdFeB磁体强度和韧性研究现状

烧结NdFeB永磁材料具有磁性能高、价格低、生产工艺简单等突出优点，因而自其开发以来，生产和应用取得了快速发展，并且其市场还将不断扩大。但是，这种材料强度和韧性差，机械加工困难，应用过程中容易开裂。因此，改善烧结NdFeB永磁材料的力学性能已成为一个迫切的需要。综述了该种材料的断裂机制及在改善材料强度和韧性等方面所做的研究工作，认为通过添加合金元素，韧化晶界，细化主相晶粒，是一种有效的方法。研究表明，材料的断裂方式主要为沿晶断裂，晶界上的薄片富Nd相是引起沿晶断裂的主要原因，通过微量添加合金元素能有效改善磁体力学特性。     

日本放电等离子体烧结的现状

放电等离子烧结是通过粉末颗粒之间的等离子体放电,并对粉末加热加压进行烧结,制取高性能材料的一种新的粉末冶金技术.具有升温速度快、烧结时间短、组织结构可控、节能环保等鲜明特点.本文简介了日本近年来放电等离子烧结的现状,包括设备、模具、制备的材料.希望能对该领域的同行有参考意义.     

沿晶渗碳体网断裂机制的研究

对轴承钢研磨裂纹的成因和消除途径进行了研究,渗碳体层越厚,越容易产生研磨裂纹。控制好终轧温度和轧后冷速,使之不形成较厚的Fe3C网,可以防止研磨裂纹的产生。     

微波烧结YG12硬质合金脱碳的控制

通过在混合料中增加炭黑和在填料中添加炭黑两种方法,来抑制微波烧结YG12硬质合金在微波烧结过程中出现的脱碳现象,从而提高微波烧结硬质合金的性能.结果表明:在混合料中添加炭黑可以抑制合金的脱碳行为,当炭黑添加量为0.4％(质量分数)时,合金的抗弯强度较理想,合金抗弯强度可达2 250 MPa;而通过在填料中添加炭黑有效抑...     

烧结NdFeB磁体表面化学镀Ni-Cu-P合金及防腐性能

在烧结NdFeB磁体表面化学镀Ni-Cu-P以提高其耐腐蚀性能.研究了络合剂的质量浓度、镀液的pH值、施镀温度及金属离子配比[Cu²⁺]/[Ni²⁺]对沉积速度和镀层成分的影响.用扫描电镜(SEM)和能谱仪(EDAX)观察镀层形貌并分析镀层成分.测定Ni-Cu-P合金镀层在质量分数3.5%NaCl溶液中的极化曲线,并结合中性盐雾实验表征镀层的耐腐蚀性能.研究表明:烧结NdFeB永磁体经碱性超声波除油、酸洗活化后进行化学镀Ni-Cu-P,可得到结合力良好的合金镀层;随着镀液中金属离子配比[Cu²⁺]/[Ni²⁺]的增大,所得镀层从非晶向晶态转变,镀层中的磷含量先升高后降低,镀层表面变得平整、致密;化学镀Ni-Cu-P三元合金的耐腐蚀性能优于相同条件下所得到的Ni-P镀层,且从金属离子配比([Cu²⁺]/[Ni²⁺])为0.02的镀液中得到的镀层的耐腐蚀性能最强.     

放电等离子烧结TiAl基合金的显微组织及力学性能

以Ti-47.5Al-2.5V-1.0Cr合金粉末为原料,采用放电等离子烧结工艺制备出TiAl基合金,并研究了制备工艺、显微组织与室温力学性能三者的关系.结果表明,采用放电等离子烧结方法可制备出致密度高、组织均匀的TiAl基合金.烧结温度对合金的显微组织影响显著,且其室温力学性能与显微组织密切相关,显微组织越细小,室温强度和塑性越高.当烧结温度为1100℃时,制备出的TiAl-V-Cr合金显微组织类型为细小双态组织,具有35.2%的压缩率和3321MPa的断裂强度,显示出较好的室温压缩性能.     

烧结NdFeB永磁合金本征腐蚀特性研究进展

介绍了近年来有关烧结NdFeB永磁合金的腐蚀机理及其本征腐蚀特性方面的研究进展情况,着重评述了合金化和显微组织结构对磁体腐蚀特性的作用机制及效果,并在此基础上提出了一些改进措施.     

Microstructural evolution and mechanical properties of AlCrFeNiCoC high entropy alloy produced via spark plasma sintering

AlCrFeCoC high entropy alloy was synthesised through mechanical alloying and spark plasma sintering. The milling time had a strong influence on the particles shape and structure and consequently on microstructural and mechanical evolution of the material after sintering. The material's microstructure after spark plasma sintering contained FCC and BCC phases as well as ordered BCC and C₂₃C₆ carbide. The material's strength increased with increasing the milling time because of the finer microstructure and phases formation evolution.     

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...     

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 bulk Sm2 Fe17 Nx sintered magnets prepared by spark plasma sintering

Abstract

Sm₂Fe₁₇N_x sintered magnets were fabricated by spark plasma sintering (SPS) technique. Effects of sintering pressure, sintering temperature and heating rate on the magnetic properties and crystal structures of the magnets were investigated. The results showed that the density of the magnet was obviously improved with increasing sintering pressure, but the coercivity dropped simultaneously because Sm₂Fe₁₇N_x decomposed into SmN, α-Fe and N₂. The coercivity decreased rapidly when sintering temperature was above 200°C under 1 GPa sintering pressure, which indicated that high pressure promoted the decomposition of Sm₂Fe₁₇N_x even at low temperature. In addition, the decomposition could not be effectively restrained even if the heating rate reached 450°C min^?1.     

放电等离子烧结法制备高导热金刚石/Al复合材料

以金刚石颗粒和铝粉为原料,通过放电等离子烧结(spark plasma sintering,SPS)制备高导热金刚石/Al复合材料,在烧结前采用真空微蒸发镀钛工艺对金刚石颗粒进行表面金属化,以降低复合材料的界面热阻.研究SPS工艺参数、铝粉粒度搭配以及复合材料中金刚石含量(体积分数)等对该复合材料致密度及热导率的影响....     

放电等离子烧结法(SPS)制备Co-Mn复合材料的研究

采用SPS烧结法在800℃、45 MPa下烧结32 min制得微观组织理想的Co-Mn复合材料,并结合烧结过程中出现的样品部分熔化及烧结孔缺陷等问题,简要引用分子运动学相关知识,重点探讨并分析SPS烧结理论与实际烧结过程的拟合程度,以达到完善SPS烧结理论在实际生产中应用的目的。     

烧结Nd-Fe-B的力学性能研究进展

烧结Nd-Fe-B磁体属于脆性材料,力学性能是其综合性能的一个重要指标。磁体力学性能及加工性能的好坏,直接影响其服役可靠性和生产企业的制造成本。国防、航空等应用领域对磁体的抗冲击过载性能提出了很高的要求。分析了烧结Nd-Fe-B磁体的力学特性特征,重点介绍了改善力学性能研究所取得的成果,并展望了其未来的发展方向。