检索结果-南通市图书馆

Corrosion prevention of sintered nd-fe-b magnet by a phosphate chemical conversion treatment

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2021年第1期40卷 185-189页

作者： Xia Ding Xiu-Chun Wang Kai-Hong Ding Sheng-Li Cui Yong-Cong Sun Mu-Sen Li Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials Ministry of EducationShandong UniversityJinan 250061China New Material Institute of Shandong Academy of Sciences.Jinan 250014 China Yantai Shougang magnetic Materials Inc Yantai 265500China

The corrosion-resistant coating formed on the surface of sintered nd-fe-b magnet by a phosphate chemical conversion(PCC)treatment was *** morphology,phase composition and thickness of the coating were investigated by field emission scanning electron microscopy(fe-SEM),energy-dispersive spectrometer(EDS),Fourier transform infrared(FTIR)spectrometer and coating thickness *** corrosion behaviour of the phosphated magnet was evaluated by copper sulphate spot test,neutral salt spray test and electrochemical potentiodynamic polarization *** magnetic properties of the phosphated magnet were also *** experimental results show that the phosphate coating has such characteristics as dense granular growth,uniform distribution and thickness range of 10-18μ*** corrosion resistance of the magnet is significantly improved by phosphate coating without losing magnetic ***,this highly efficient PCC was a good way for increasing the corrosion resistance of the sintered nd-fe-b magnets.

关键词： nd-fe-b magnet Phosphate chemical conversion Microstructure Corrosion resistance

Effect of annealing temperature on magnetic properties of a sintered nd-fe-b magnet after grain boundary diffusion with Dy_(70)Cu_(30) alloy

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2024年第1期42卷 116-120,I0004页

作者： Ruipeng Qian Yuxuan Ma Fugang Chen Hui Sun Yong Zhao Yunlong Chen School of Materials Science and Engineering Jiangsu University of Science and TechnologyZhenjiang212003China School of Energy and Power Engineering Jiangsu University of Science and TechnologyZhenjiang212003China

Grain boundary diffusion process(GbDP)has been developed as an effective approach to increase the coercivity of sintered nd-fe-b magnets by regulating the compositions and phase distributions near grain *** work aims to explore how to select the optimum annealing temperature after *** this work GbDP was performed on a sintered nd-fe-b magnet using Dy_(70)Cu_(30) *** GbDP the low eutectic temperature of the grain boundary phases decreases from the initial 492 to 451℃.The magnetic property dependent on different annealing temperatures near the low eutectic temperature was *** magnetic properties,especially the squareness factor of demagnetization curve show a strong dependence on the annealing *** GbDP the optimal magnetic properties can be obtained after annealing just above the low eutectic temperature of the grain boundary *** mechanism is discussed based on the microstructure analysis.

关键词： nd-fe-b magnet Grain boundary diffusion Annealing Dy_(70)Cu_(30)alloy Rare earths

Coercivity Mechanism of Melt-spun nd-fe-b bonded magnet

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 1990年第4期6卷 272-276页

作者：黄钢祥徐庆镇高惠民余善富华宏慈王葛亚 Shanghai Iron and Steel Research Institute Shanghai200940China. Shanghai Institute of Metallurgy Academia SinicaShanghai200050China.

The microstructures of melt-spun nd_135- fe_81.74b4.76 ribbons have been investigated by means of X-ray diffraction,Mossbauer spectroscopy and *** results show that optimal magnetic properties of the bond- ed magnet can be obtained by melt-spun alloys at wheel velocity of 24m/s,the microstructure of which was single phase nd_2fe_(14)b crystallites,and no other phases,such as nd-rich,b-rich or x-fe phase,were *** is considered that the high intrinsic coercivity ~iH_c can be attributed to the sin- gle-domain behaviour of nd_2fe_(14)b crystallite phase.

关键词： coercivity nd-fe-b magnet

Grain Growth behavior in Sintered nd-fe-b magnets

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2007年第3期25卷 329-335页

作者：刘湘涟周寿增 School of Mechanical Engineering Ningbo University of Technology State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing

The nd2fe14b grain growth behavior in sintered nd-fe-b magnets was quantitatively *** effects of sintering temperature and time,and alloy powder size and its distribution on grain growth process were ***,possible grain growth mechanisms in these magnets were qualitatively *** nd2fe14b grain growth proceeded at quite a high rate in the initial 0~1 h of sintering and from then onwards the grain growth rate decreased.A large average particle size or a wide particle size distribution of initial alloy powders was found to remarkably accelerate the grain growth process and even result in the occurrence of abnormal grain *** the basis of experimental results,two grain growth mechanisms were considered to operate during sintering of nd-fe-b magnets,that is,dissolution and re-precipitation of nd2fe14b particles,and nd2fe14b particle growth by *** was believed that nd2fe14b particle growth by coalescence not only produced a large average grain size and a wide grain size distribution,but also was the fundamental reason for the formation of abnormally large grains in the microstructure of sintered nd-fe-b magnets.

关键词： nd-fe-b magnet sintering grain growth powder size rare earths

Microstructure and magnetic properties of anisotropic nd-fe-b magnets prepared by spark plasma sintering and hot deformation

在线全文

学校读者我要写书评

暂无评论

Transactions of Nonferrous Metals Society of China 2014年第10期24卷 3142-3151页

作者：李小强李力胡可陈志成屈盛官杨超华南理工大学国家金属材料近净成形工程技术研究中心广州510640

bulk anisotropic nd-fe-b magnets were prepared from hydrogen-disproportionation-desorption-recombination（HDDR） powders via spark plasma sintering（SPS） and subsequent hot deformation. The influence of sintering temperature on the structure and magnetic properties of the spark plasma sintered nd-fe-b magnets were studied. The remanence br, intrinsic coercivity Hcj, and the maximum energy product（bH）max, of sintered nd-fe-b magnets first increase and then decrease with the increase of sintering temperature, TSPS, from 650 °C to 900 °C. The optimal magnetic properties can be obtained when TSPS is 800 °C. The nd-fe-b magnet sinter treated at 800 °C was subjected to further hot deformation. Compared with the starting HDDR powders or the SPS treated magnets, the hot-deformed magnets present more obvious anisotropy and possess much better magnetic properties due to the good c-axis texture formed in the deformation process. The anisotropic magnet deformed at 800 °C with 50% compression ratio has a microstructure consisting of well aligned and platelet-shaped nd2fe14 b grains without abnormal grain growth and exhibits excellent magnetic properties parallel to the pressing axis.

关键词： nd-fe-b magnet hydrogen-disproportionation-desorption-recombination(HDDR) spark plasma sintering hot deformation magnetic property

Enhanced magnetic properties in chemically inhomogeneous nd-Dy-fe-b sintered magnets by multi-main-phase process

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2021年第5期39卷 558-564页

作者： Xiaolian Liu Mengjie Pan Pei Zhang Tianyu Ma Lizhong Zhao Lingwei Li College of Materials&Environmental Engineering Hangzhou Dianzi UniversityHangzhou 310018China State Key Laboratory of Silicon Materials Key Laboratory of Novel Materials for Information Technology of Zhejiang ProvinceDepartment of Materials Science and EngineeringZhejiang UniversityHangzhou 310027China

Homogeneous substitution of Dy for nd in the hard magnetic 2:14:1 phase can effectively enhance coercivity to ensure the high temperature operation,however,inevitably deteriorate remanence at *** this work,we performed a comparative investigation of the two magnets prepared by multimain-phase(co-sintering nd_(2)fe_(14)b and(nd,Dy)_(2)fe_(14)b powders)and single-main-phase(sintering(nd,Dy)_(2)fe_(14)b powders)*** comparative investigation reveals that at the same Dy substitution level(2.16 wt%),such chemically inhomogeneous multi-main-phase magnet possesses better roomtemperature magnetic properties as well as thermal stability than those of the single-main-phase one with homogenous Dy distribution in the matrix ***-temperature magnetic properties H_(Cj)=1664 kA/m,b_(r)=1.33 T and(bH)_(max)=350.4 kJ/m^(3)for the multi-main-phase magnet are all better than those for the single-main-phase magnet with H_(Cj)=1536 kA/m,b_(r)=1.29 T and(bH)_(max)=318.4 kj/m^(3).In addition,over the temperature range from 295 to 423 K,both the temperature coefficients of coercivity and remanence for the multi-main-phase magnet are also lower than that for the single-main-phase *** superior magnetic performance is attributed to the short-range magnetic interactions inside individual 2:14:1 phase grains and the long-range magnetostatic interactions between adjacent grains with inhomogeneous Dy *** work provides a feasible approach of enhancing coercivity and retaining energy product simultaneously in the nd-Dy-fe-b permanent magnets.

关键词： Permanent magnet nd-fe-b magnet Multi-main-phase magnetic properties Thermal stability Microstructure

magnetic properties and microstructure of nanocrystalline bulk nd-fe-b with Ce-Co addition

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2021年第6期39卷 689-695,I0003页

作者： Yilong Ma Qiqi Yang Xiaoli Chen Ying He Wenbo Xiang Jiaqi Lai bin Shao Donglin Guo Dengming Chen Kejian Li College of Metallurgy and Materials Engineering Chongqing University of Science and TechnologyChongqing 401331China The Center of Material Analysis and Testing Chongqing University of Science and TechnologyChongqing 401331China

The influence of Ce-Co alloy addition and sintering holding time on permanent magnetic properties and micro structure of nanocrystalline nd-fe-b bulk alloy were *** coercivity of nd-fe-b bulk alloy can be enhanced greatly by more than 100% after adding Ce-Co ***,when the concentration of Ce-Co is up to 30 wt%,the density of the magnet can reach the maximum value of 7.58 g/cm^(3),but the coercivity does not increase *** the other hand,with the increase of holding time to 10 min,the density and coercivity of magnets increase gradually,reaching up to 7.55 g/cm^(3) and 1134.3 kA/m,*** the addition of Ce-Co alloy,Ce-Co may easily diffuse into the nd-fe-b matrix during hot-pressing and under the high pressure and temperature,thus increasing the content of grain boundary phase and the pinning effect of grain boundary,which leads to the increase of *** extension of the hot-pressing holding time may be more conducive to the diffusion of CeCo into the nd-fe-b *** addition,the effect of Ce-Co addition on the magnetic properties of nd-feb with different content of rare earth was also *** addition of Ce-Co can effectively increase the coercivity of nanocomposite nd_(2)fe_(14)b/α-fe *** addition of Nb to the parent alloy can further improve the *** nd_(11)fe_(81.5)Nb_(1)Ga_(0.5)b_(6) alloy with 10 wt% Ce-Co addition,the coercivity can increase from 740.28 to 1098.48 kA/m.

关键词： nd-fe-b magnet Ce-Co addition Coercivity Microstructure Nanocomposite Rare earths

THE EFfeCT OF Mo ADDITION ON COERCIVITY OF ndfeb SINTERED magnet PREPARED bY bLEndING METHOD

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2005年第4期18卷 557-560页

作者： J.Q. Zhou M.G. Zhang Department of Materials Engineering Taiyuan University of Science and TechnologyTaiyuan 030024 China

Alloy modification, accompanying with proper heat treatment, is commonly used to improve the thermal stability of ndfeb magnet. Traditional alloy modification is performed through melting process with alloy elements to form the multi-alloy. In doing so, these alloy elements not only are introduced into the inter-ranular boundaries, but partly into the main phase, thus decreasing to some extent the magnetism of the main phase. In this paper, the blending method is used to prepare the nd22fe71b7/Mo sintered magnet, and its magnetic properties and microstractures are investigated. The results show that by adding 1.5% （mass fraction） Mo, the intrinsic coercivity 24, of the magnet reaches the maximum value of 1719.36KA/m, while continually increasing the amount of Mo has a less effect on iHc Microstructures analysis indicates that Mo-free nd-fe-b magnet has not uniform grains in size, while that with Mo element has uniform grains in size and smooth grain boundaries. Experiments show that after the ndfeb magnet is sintered at 1273K and annealed at 873K, the added Mo element could prevent the equilibrium transformation between the main phase and nd-rich phase, thus resulting in the precipitation of fine second main phase （nd2fe14-xMoxb） from the main phase boundaries, preventing the nucleation and expansion of anti-magnetic domain, and enhancing the coercivity.

关键词： nd-fe-b magnet microstructure coercivity