镀铜/镍烧结钕铁硼永磁体与DP1180钢钎焊接头的组织与性能

采用Zn-6Sn-5Bi钎料对镀Cu/Ni的烧结NdFeB永磁体和DP1180钢进行钎焊连接,对比分析了2种镀层条件下钎焊接头的微观组织和力学性能。结果表明,对于镀Cu的烧结NdFeB永磁体和DP1180钢的钎焊接头,Cu在钎料中扩散并与Zn、Fe反应生成脆性金属间化合物,导致钎缝中出现裂纹和孔洞。与无镀层时的烧结NdFeB永磁体和DP1180钢的钎焊接头相比,接头的剪切强度由61.9 MPa降低至52.3 MPa;对于镀Ni的烧结NdFeB永磁体和DP1180钢的钎焊接头,Ni集中分布在NdFeB一侧的界面处,并且由于Sn和Bi的扩散形成了不同的扩散层,其剪切强度提高至78.1 MPa。     

Cr对Ni-P系钎料钎焊不锈钢接头性能的影响

研究了钎焊温度对Ni-P系钎料铺展件能及其真空钎焊OCr13不锈钢接头力学性能的影响.结果表明,Ni-P系钎料铺展面积随钎焊温度的升高而增大,并且相同温度下不含Cr的Ni-P钎料铺展面积大于Ni-Cr-P的铺展面积;钎焊温度从925℃升高到1000℃过程中,Ni-P、Ni-Cr-P钎料钎焊不锈钢接头的室温剪切强度均增大,并且在相同钎焊工艺下,不含Cr的Ni-P钎料钎焊不锈钢接头室温剪切强度优于Ni-Cr-P钎焊接头强度30～40MPa;Ni-P系钎料钎焊接头高温强度随温度升高而下降,测试温度超过500℃时,相同温度下含Cr的钎料能够提高钎焊接头强度0～30 MPa.     

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。     

Sn-9Zn-xRE钎料钎焊6061铝合金接头性能研究

在Sn-9Zn合金的基础上添加了(0.1~0.4)wt%的混合稀土(La、Ce)。使用Sn-9Zn-xRE钎料对6061铝合金在空气炉中钎焊,接头的抗剪切强度得到显著提高。当稀土元素添加量为0.2 wt%时,强度由12.88 MPa上升至最大值16.73 MPa,强度提高约30%。通过能谱分析发现,在钎料与母材的界面形成了以Al为基的Al、Zn固溶体,并且钎料中的Zn向母材进行了扩散。     

TiNiB高温钎料钎焊TiAl基合金接头微观组织

采用电弧熔炼TiNiB合金作为高温钎料对TiAl合金进行钎焊,研究了接头界面组织的形成及其随钎焊温度变化的演化过程.电弧熔炼的TiNiB合金钎料主要由Ti-Ni与TiNi3共晶组织及弥散分布的块状TiB2组成,DTA测试曲线表明钎料的熔点为1 120℃.钎焊过程中,TiAl基体向液态钎料中的溶解量决定了钎焊接头界面组织的形成及其演化过程.随着活性元素Ti和Al向液态钎料溶解量的增加,靠近钎缝侧的TiAl基体发生固态相变转化为β层;钎缝组织演化为Ti-Al-Ni三元化合物,并伴有少量的β相;块状的TiB2在过量活性元素Ti存在的情况下逐渐转变为长条状的TiB相.     

不锈钢薄板搭接激光软钎焊接头组织与性能

采用激光对304不锈钢薄板搭接缝进行软钎焊,并对钎缝组织与力学性能进行了研究.工艺试验结果表明,当激光束倾角为60°和离焦量为300 mm时,能够有效降低激光束的热输入,实现304不锈钢薄板搭接缝的无变形钎焊,填缝深度可达5 mm,钎缝外观成形光滑、饱满,颜色与母材相近,无需涂装.钎焊接头分为不锈钢母材区、钎缝区、不锈钢母材区3个区域,钎缝区和母材区的边界清晰且明显,钎缝组织连续致密,无气孔、裂纹等缺陷.钎缝显微组织主要由黑色固溶体相、大菱形块状白色相和短棒状白色相组成,分析认为3种相分别为锡基固溶体相、SnSb相和Cu₆Sn₅相.钎料和母材之间形成约1～2μm金属化合物FeSn₂扩散层.钎缝的平均抗剪强度测试结果为39 MPa,能够满足不锈钢薄板搭接缝的工程应用.     

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.     

铝基活性钎料真空钎焊C_f/C复合材料焊接接头的组织及性能

用铝基活性钎料对C_f/C复合材料进行真空钎焊,并对接头的微观组织、形成机理和接头强度进行了试验研究.结果表明,使用铝基活性钎料可以实现C_f/C复合材料的连接,且在试验温度范围内,接头强度随钎料成分不同而发生变化.电子探针观察表明,钎料与C_f/C复合材料钎焊接头润湿性良好,存在成分偏聚层,这种层状结构对缓和焊接残余应力十分有利.室温下接头最高剪切强度可达16MPa.     

高压技术对烧结NdFeB性能和微观结构的影响

采用高压和常规压制方式制备了烧结(PrNd)33Al0.7Nb0.6Cu0.1B1.05Febal(质量分数)永磁体,利用扫描电镜、金相显微镜和振动样品磁强计及维氏硬度计对比研究了两种压制方式对样品微观组织和性能的影响。结果发现:与常规压制方式制备样品相比,1.8GPa压强成型制备样品的Hcj和(BH)max分别提高了133kA.m-1和0.6kJ.m-3;而3.6GPa压强成型制备样品的Hcj和(BH)max分别提高了120.3kA.m-1和3.2kJ.m-3。高压样品的主相晶粒较细小,富稀土相分布均匀合理,但过高的压强将使其维氏硬度降低。     

烧结NdFeB永磁体表面微弧氧化涂层的制备及性能

为了提高烧结NdFeB永磁体的耐蚀性,本文在铝酸盐溶液中采用二步微弧氧化工艺在烧结NdFeB永磁体表面制备了氧化铝陶瓷涂层。微弧氧化过程中,电压-时间曲线可大致分为四个阶段,与阀金属处理的曲线基本一致。烧结NdFeB表面制备的涂层呈现出典型的微弧氧化多孔形貌,厚度大约为5 μm。涂层中仅含有Al₂O₃结晶相,并含有少量的Fe、Nd和P元素。微弧氧化处理后,烧结NdFeB的表面粗糙度有所增加,耐蚀性较基体提高了1个数量级。然后,微弧氧化处理后,烧结NdFeB磁体的剩磁和最大磁能积较未处理NdFeB有所下降。     

Primary investigation of corrosion resistance of Ni-P/TiO2 composite film on sintered NdFeB permanent magnet

In this paper, an electroless nickel plating and sol-gel combined technique used to prepare the Ni-P/TiO₂ composite film on sintered NdFeB permanent magnet is described and the composite film was characterized by X-ray diffraction (XRD), environmental scanning electron microscopy (ESEM), and energy dispersive X-ray spectrometer (EDX). The corrosion resistance of Ni-P/TiO₂ film was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The self-corrosion current density (i_corr) of Ni-P/TiO₂ composite film is 2.38μA/cm² in 0.5mol/L H₂SO₄ solution about 33% of that of Ni-P coating and 0.22μA/cm² in 0.5mol/L NaCl solution about 14% of that of Ni-P coating, respectively. In 0.5mol/L H₂SO₄ and 0.5mol/L NaCl solutions, the polarization resistance (Rp) of the composite film is 12.5kΩ cm² and 120kΩ cm², about 1.6 and 2 times that of Ni-P coating, respectively. The results indicate that Ni-P/TiO₂ composite film has a better corrosion resistance than Ni-P coating.     

Corrosion resistance and mechanical properties of pulse electrodeposited Ni–TiO2 composite coating for sintered NdFeB magnet

Ni–TiO₂ composite coating which was prepared under pulse current conditions was successfully performed on sintered NdFeB magnet. As a comparison, pure nickel coating was also prepared. The phase structure, the surface morphology, the chemical composition, the anti-corrosion performance of the coatings for magnets, the microhardness and the wearing resistance performance of the coatings were studied using X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), electrochemical technique, Vickers hardness tester and ball-on-disc tribometer, respectively. The results revealed that Ni–TiO₂ composite coating provided excellent anti-corrosion performance for the magnets, and showed higher microhardness and better anti-wear performance.     

Improving adhesion of electroless Ni-P coating on sintered NdFeB magnet

The poor adhesion of Ni-P coatings on sintered NdFeB magnets imposes a great challenge in industrial applications. In this work, a kind of Zn phosphate film was fabricated on NdFeB sintered magnets surface to enhance the adhesion strength between the Ni-P coating and the substrate. The results showed that the adhesion strength between magnet surface and Ni-P coating was enhanced from 2.3 MPa to 10.1 MPa after Zn phosphating treatment. The addition of the phosphate created a protective layer over the substrate and inhibited the dissolving of the substrate and generation of H₂, which deteriorated the mechanical strength of the substrate and led to lower adhesion strength. On the other hand, the pores and micro-cracks on the phosphate film enhanced the interfacial contact area as well as reinforced the anchoring of Ni-P grains through the pinning effect, thus leading to high adhesion strength between Ni-P and magnet substrate. Phosphating solution composition and process were also optimized by orthogonal experiments in this work.     

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。     

Research and development of rare earth permanent magnets in China

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Corrosion resistance of environment‐friendly sealing layer for Zn‐coated sintered NdFeB magnet

In this paper, a protective sealed Zn coating (SZC) was prepared on sintered NdFeB magnet by the combination of electrodeposition and sol–gel method. The unsealed Zn coating (UZC) was also studied for a comparison. The surface morphology of UZC and the cross‐section morphology of SZC were investigated using scanning election microscope (SEM). The microstructure of Zn coating and structure of sealing layer were studied by X‐ray diffraction (XRD) and Fourier transform infrared (FT‐IR) spectrum, respectively. The corrosion characteristics of SZC and UZC in neutral 3.5 wt% NaCl solution were evaluated using electrochemical measurements including open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization test, indicating that the anticorrosive properties of SZC coated specimens increased 20 times compared with that of UZC coated specimens. In order to further investigate the anticorrosive properties of SZC, a long‐term immersion test was carried out in neutral 3.5 wt% NaCl solution using EIS. The results of long‐term corrosion test showed that the SZC could provide long‐term protection in neutral 3.5 wt% NaCl solution for NdFeB magnet.     

钕铁硼永磁材料在微特电机中的应用

介绍钕铁硼永磁材料的性能特点及其在微特电机中的应用研究，简要阐述了钕铁硼永磁材料在微特电机中的应用概况，指出钕铁硼永磁在微特电机中的应用具有广阔的发展前景。     

烧结NdFeB永磁材料的力学性能及断裂行为的各向异性

对从同一磁体上切取取向不同的3组烧结NdFeB试样进行抗弯强度测定，对其抗弯断口进行宏观观察和SEM观察。对烧结NdFeB永磁材料的力学性能和断裂行为的各向异性进行了研究。研究结果表明：烧结NdFeB永磁材料的抗弯强度和断裂行为具有明显的各向异性。不同取向方向试样断裂的微观机制都主要为沿晶断裂。当取向方向沿抗弯试样的长度方向时，在断口上发现了明显的穿晶解理断裂，且该组试样的抗弯强度值明显低于沿其它两个方向取向的试样。