Sm2Fe17和Sm10.5Fe88.5Zr1.0的氮化行为

通过真空电弧炉制备了Sm2Fe17和Sm10.5Fe88．5Zr1．0母合金，铸态Sm2Fe17先经均匀化处理后再氮化．而Sm10.5Fe88．5Zr1．0则不经均匀化退火而直接在高纯氮气中氮化。运用扫描电子显微镜和X射线衍射技术对其氮化行为进行了研究。薄片扩散实验表明氮在Sm2Fe17中的扩散要比在Sm10.5Fe88．5Zr1．0中的扩散快。运用Fick第二定律通过理论计算得出直径为20μm的Sm2Fe17合金和Sm10.5Fe88．5Zr1.0合金球形粉末粒子，实现充分氮化的时间为10h和16h。实际粉末实现完全氮化的时间要比理论计算的时间少。这和粒径分布、颗粒表面状态、氮化过程产生的微裂纹以及实际条件和理想条件的差异有关。对于直径为20μm的粉末，氮化时间为6h时氮化已基本完成，氮化时间过长．Sm2Fe17Nx会发生分解。     

Comparative investigation of the nitrogenation mechanisms of bulk intermetallic Sm2(Fe,Co)17 by two processes

The nitrogenation mechanisms of the Sm₂(Fe_0.5Co_0.5)₁₇ compound were investigated on bulk samples using X-ray diffraction and chemical analysis. Two nitrogenation processes (fluidized bed nitrogenation (FBN) and gaseous nitrogenation (GN)) were used in order to compare the different steps occurring during the treatment. The fluidized bed process leads to a constant nitrogen surface concentration after one hour treatment while the concentration increases continuously with the gaseous process. The overall bulk nitrogenation kinetics is parabolic for the fluidized bed, whereas the gaseous nitrogenation exhibits first an incubation period followed by an accelerated rate. Two different mechanisms, bulk diffusion for the FBN process and an interface reaction for the GN process, govern the nitrogenation kinetics.     

Structural change in Sm2Fe17 alloys during homogenization and HD processing

The evolution of phase compositions, phase change and microstructure in Sm₂Fe₁₇ alloys during anneal and hydrogenation–disproportionation processing has been studied systematically using X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The results indicate that, after annealing at 1050 °C for 24 h, the main phase in the as-homogenized ingot is Sm₂Fe₁₇ with a rhombohedral Th₂Zn₁₇-type structure, together with a negligible amount of α-Fe phase. A minor phase, SmFe₃/SmFe₂, is barely detectable. The Sm₂Fe₁₇ alloy first absorbs the hydrogen in the hydrogenation atmosphere with a pressure of 0.1 MPa. Disproportionation begins at T ≥ 500 °C, and large amounts of SmH_x and α-Fe phases are formed, partly in microcrystalline or amorphous structures. As the temperature increases, the microcrystals and amorphous structures transform into a fully crystalline structure, the transformation becoming complete at 750 °C. The resultant crystal grain size is about 50–100 nm.     

HDDR处理的Sm2Fe16.5Ti0.5合金的结构与氮化

采用HDDR及氮化工艺制备了Sm2Fe16.5Ti0.5Ny粉末.铸态Sm2Fe16.5Ti0.5合金存在择优取向,Sm2(Fe,Ti)17主相的214衍射峰增强.均匀化退火后,只有约0.6%的α-Fe(Ti)相与主相Sm2(Fe,Ti)17共存.经不同循环的HDDR工艺处理后,物相组成不发生变化,但α-Fe(Ti)相含量增加.HDDR工艺有助于获得细晶结构,提高磁粉的矫顽力.HDDR处理的合金的氮化由初期的Sm-Fe-Ti合金与氮快速反应阶段及后期氮在合金中的均匀化扩散阶段组成.随着氮化时间的延长,富铁相含量增加.氮化物中Sm2(Fe,Ti)17Ny主相的晶格膨胀行为由HDDR与氮化工艺共同决定.在500℃氮化2h后,796kA/m最大外场下得到的最大矫顽力为164.9kA/m,氮化12h时后得到最大剩磁45.7Am2/kg.     

Hydrogen absorption and desorption in Nd2Fe17 and Sm2Fe17

The uptake of hydrogen by Nd₂ Fe₁₇ and Sm₂Fe₁₇ has been monitored in a thermopiezic analyser as a function of temperature at an initial pressure of 1 bar (10⁵ Pa). The first stage of hydrogen absorption around 250° C yields R₂Fe₁₇H _y (R = Nd, Sm) withy 2.2; this compound retains the Th₂Zn₁₇ structure of the starting alloy but the cell volume is increased by about 3%. The Curie temperature increases from 57 to 175° C for R = Nd and from 115 to 253° C for R = Sm. A second stage of hydrogen absorption at about 600° C corresponds to disproportionation of the alloy into -Fe + RH_2–.     

Chemical Interaction between Sm2Fe17 and Ammonia

The interaction between Sm₂Fe₁₇ and ammonia in the presence of NH₄Cl (10 wt % relative to Sm₂Fe₁₇) as an activator is studied at initial NH₃ pressures from 0.6 to 0.8 MPa and temperatures from 150 to 500°C. The results indicate that, depending on the reaction temperature in the Sm₂Fe₁₇–NH₃ system, both hydriding of the parent intermetallic phase and disproportionation resulting in the formation of another hydride phase may occur. The reaction products are found to consist of fine particles. The magnetic properties of the products of Sm₂Fe₁₇ nitriding in ammonia are studied.     

Sm2Fe17Nx永磁材料的研究进展

综述了目前Sm2Fe17Nx化合物及Sm2Fe17Nx磁粉的制备方法，以及Sm2Fe17Nx化合物渗氮过程的条件选择．并进一步指出了Sm2Fe17Nx磁粉的发展现状和趋势。     

57Fe Mossbauer effect studies of Sm2Fe17 under different heat treatment conditions

Room-temperature 57Fe Mossbauer spectra have been measured in Sm2Fe17 under different heat treatment conditions. The details of fitting these spectra is exhaustively discussed. The spectra of Sm2Fe17 are split into seven inequivalent magnetic sites. An identical result was obtained by using two fitting modes. The following has been indicated from the results for all samples. Firstly for these samples containing α-Fe sextets and paramagnetic doublets, by choosing an appropriate annealing system, the smallest amount of impurities might be obtained, i.e. an approximately single-phase Sm2Fe17 compound was obtained. Secondly the overall weighted average fields were all approximately equal. This was thought to arise because the different heat treatment conditions caused no change in the near-neighbour coordination of iron atoms. Thirdly the 6c site and 18 h site had the largest and the smallest hyperfine fields, respectively. This revised version was published online in November 2006 with corrections to the Cover Date.     

快淬和退火对Fe_(83)Ga_(17)Ce_(0.8)合金结构和磁致伸缩性能的影响

采用电弧熔炼法制备了稀土Ce掺杂的Fe83Ga17Ce0.8铸态合金,然后对其进行快淬处理,获得Fe83Ga17Ce0.8快淬态合金,最后对Fe83Ga17Ce0.8快淬态合金在1 223K下进行退火热处理5h。用X射线衍射(XRD)、扫描电镜及能谱仪(SEM/EDS)和磁致伸缩测试方法研究了快淬和退火对合金结构和磁致伸缩性能的影响。结果表明,Fe83Ga17Ce0.8铸态合金由bcc结构的Fe(Ga)相和少量的CeFe2第二相组成。Fe83Ga17Ce0.8快淬态合金除了含有大量的Fe(Ga)相和少量的CeFe2相外,合金中还出现了非对称DO3结构的Fe3Ga相。Fe83Ga17Ce0.8快淬态合金经退火热处理后,合金中的CeFe2相转化为贫稀土Ce2Fe17相。在外磁场为557kA/m时,Fe83Ga17Ce0.8快淬态合金的磁致伸缩系数(3.82×10-4)明显大于铸态合金(3.56×10-4)和退火态合金(1.82×10-4)的磁致伸缩系数。     

Studies on structural transformation and magnetic properties in Sm2Co17 type alloys

Structural transformations and microstructural characterisation of Sm₂Co₁₇ alloys containing Fe, Cu and Zr at different stages of thermal processing have been investigated by X-ray diffraction, optical, scanning electron and transmission electron microscopes. Solution treated samples consist of a mixture of hexagonal TbCu₇ (1:7 H) and rhombohedral Th₂Zn₁₇ (2:17 R) structure types of 2:17 phase. After isothermal aging, TbCu₇ + Th₂Zn₁₇ structures transform into Th₂Zn₁₇ type structure with precipitation of Cu-rich hexagonal SmCo₅ (1:5 H) and Zr-rich platelet phases. In addition to the main phases, a soft magnetic phase of composition Zr₆(FeCo)₂₃ is formed in alloys containing higher Zr composition. Isothermal aging studies reveal that magnetic properties show a peak value when aged at 1108–1123 K for 10 h. TEM studies show cellular precipitate structure with cell interiors having 2:17 R structure, while the fully coherent cell boundaries have the 1:5 H structure. Zr-rich platelets which run across many cells and cell boundaries were found to have 1:7 H structure.     

Magnetic anisotropy in Sm2Fe17-xMx (M = Al, Ga) and (Sm1-xTmx)(2)Fe14Al3

1. IntroductionMany illtermetajlic compounds of R-Fe and R-Co(R: rare earths) have some ideal properties as highquality permanent magnet materials where a largemagnetic anisotropy of 4f electrons is coupled withstrong exchange interaction of 3d electrons via the4f-3d illteraction.In 1967 the SmCos magnet was discovered as thefirst rare earth permanent magnet, and in 1973 moreimproved magnet in the form of SmZCo17 was developed, These two compounds were found to have excellellt permanellt m…     

高性能各向异性Sm2Fe17Nx磁粉的制备

本文研究了高性能各向异性Ｓｍ２Ｆｅ１７Ｎｘ磁粉的制备工艺路线与工艺参数。优化了制备与工艺参数。已制备出磁性能达到：Ｂｒ＝１．３９Ｔ，Ｈｃｉ＝８５０ＫＡ／ｍ和（ＢＨ）ｍ＝２３６ＫＪ／ｍ＾３的各向异性Ｓｍ２Ｆｅ１７Ｎ２．８８磁粉，该磁粉的各向异性场ＨＡ达到２０Ｔ。     

合金元素对Sm2Fe17Nx微观结构和性能的影响

综述了合金元素的添加对Sm2Fe17Nx稀土永磁材料的微观结构以及性能的影响。介绍了取代元素的分类，从理论和研究现状等方面分析和总结了合金元素对Sm2Fe17Nx稀土永磁材料的热稳定性、磁性能以及工艺性能的影响规律，并对今后Sm2Fe17Nx稀土永磁材料的研究和开发提出了建议。     

合金元素对Sm2Fe17Nx微观结构和性能的影响

综述了合金元素的添加对Sm2Fe17Nx稀土永磁材料的微观结构以及性能的影响.介绍了取代元素的分类,从理论和研究现状等方面分析和总结了合金元素对Sm2Fe17Nx稀土永磁材料的热稳定性、磁性能以及工艺性能的影响规律,并对今后Sm2Fe17Nx稀土永磁材料的研究和开发提出了建议.     

Crystal structure of compounds Fe17Gd2 and Fe17Tb2

Abstract

Differential thermal analysis and dilatometry investigations of Fe–Gd alloys in the range 5–16·6 at.-% Gd showed the occurrence of a phase transformation at about 1215°C. From X-ray diffraction investigations, it was concluded that this corresponds to an allotropic change in Fe₁₇Gd₂ from the rhombohedral Zn₂Th₂ type at low temperature to the hexagonal Ni₁₇Th₂ type at high temperature. Both these structures were detected in as cast samples of Fe–Gd and Fe–Tb alloys. However, in the Fe₁₇Tb₂ compound, no transformation was detected by differential thermal analysis.

MST/1227     

高性能Sm2Fe17Nx磁粉制备关键技术研究

采用粉末冶金工艺制备了Sm2Fe17Nx永磁粉末,研究了工艺参数对Sm2Fe17合金的显微组织及Sm2Fe17Nx粉末磁特性的影响。结果表明,铸态合金的均匀化、粉末的氮化以及粉碎过程是获得高性能磁粉的关键因素。采用最佳工艺条件制备的磁粉的磁特性为：4πMr=1．24T．iHc=756kA／m,(BH)max=220kJ／m^3。     

制备Sm2Fe17Nx稀土永磁粉的工艺研究现状

综述了制备Sm2Fe17Nx稀土永磁粉的主要方法，指出对现有工艺的深入研究与不断改进，开发新工艺，开创新技术，探索出一条成熟的，经济实用的生产工艺线路，对获得高性能的Sm2Fe17Nx磁体，并使之成为具有竞争力的第四代稀土永磁体，有相当重要的意义，此外还对如何控制工艺中影响Sm2Fe17Nx磁性能的一些主要因素做了简要分析。     

The hydrogenation behaviour of the phases Sm2Co17 and Pr2Co17

The compounds Sm₂Co₁₇ and Pr₂Co₁₇ have been charged with hydrogen and the hydrogen compositions determined between pressures of approximately 2.5×10^–2 and 13 atm at temperatures of 150 and 200° C. Very low rates of hydrogen absorption were observed below 150° C so that solubility measurements have not been obtained below this temperature. The X-ray diffraction studies show that the structure of the metal lattice is unchanged by the hydrogenation process, i.e. the rhombohedral, Th₂Zn₁₇ structure type with space groupR¯3_m is maintained. As a result of the expansion the alloys become cracked and friable on hydrogenation.     

Microstructure and its correlation to magnetic properties in 2:17 type (Sm,Gd)-Co-Fe-Cu-Zr alloys

Studies on the evolution of microstructure and phase transformation at various stages of thermal processing have been carried out in 2:17 type (Sm,Gd)-Co-Fe-Cu-Zr alloys. Microstructural studies reveal that during the solution heat treatment stage, a lamellar structure is formed and its volume fraction is found to be more at 1463 K for alloys without Gd, while at 1473 K for alloys with Gd = 25 wt% of Sm. It appears that the formation of the lamellar structure is closely associated with the phase transformation from Th₂Ni₁₇ (TbCu₇ + Th₂Zn₁₇) structure during the solution heat treatment. Magnetic measurements in isothermally aged (1123 K) samples showed that the replacement of 25% of Sm by Gd reduces the energy product from 180 to 136 kJ/m³. The Gd substitution is also found to reduce the temperature coefficient of magnetisation from 350 to 225 ppm/°C in the temperature range of 30–100°C.