共查询到20条相似文献,搜索用时 625 毫秒
1.
Melt-spun Nd4.5Fe77B18.5 ribbons were prepared under various superheat temperatures.The microstructure characteristics,crystallization behavior,and subsequent magnetic properties of Fe3B/Nd2Fe14B nanocomposite magnets were investigated using X-ray diffraction,differential thermal analysis,and vibrating sample magnetometry.It was shown that melt spinning at different quenching temperatures caused the as-quenched ribbons to have distinctive crystallization behavior.Depending on superheat temperature,phase tra... 相似文献
2.
3.
A rapidly solidified Al85Y4Nd4Fe7(%, in nominal atomic fraction) alloy was prepared by melt spinning. Asquenched and as-annealed microstructures were studied by differential scanning calorimetry (DSC), X-ray diffraction(XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). Fully amorphous structure could be obtained in the rapidly solidified Al85Y4Nd4Fe7 alloy ribbons. The temperature of first crystallization exceeds 300℃. Crystallization of as-annealed Al85Y4Nd4Fe7 alloy is shown to occur in two stages : ( 1 ) primary crystallization of α-Al; (2) formation of Al3Y, Al13Fe4 and unknown crystalline phases. 相似文献
4.
The ribbons of NdFeB/α-Fe composite alloy were prepared by melt spinning and post crystallizing technique.The element distri-butions and phase component of both surfaces of as-spun ribbons were measured by energy dispersive spectrometry (EDS) and X-ray diffrac-tion (XRD).Because of the centrifugation,a segregation of B,Fe,and Nd concentrations was observed at the cross section.After crystallizing annealing,the element concentration segregation still existed in the as-crystallized ribbons.Due to the segregation of B,Fe,and Nd,the B-rich phase was observed near the wheel side surface.The B-rich phase may deteriorate the magnetic property of NdFeB/α-Fe composite alloy. 相似文献
5.
6.
The effects of different annealing conditions on the phase formation with NaZn13 structure were investigated in La(Fe1-xCox)11.9Si1.1(x=0.068) compounds. It was found that the 1:13 phase was not formed directly from the melt upon cooling but via a peritectic reaction between the pro-peritectic γ-Fe and the La-rich phase. Annealing temperature was very important for the formation of 1:13 phase. Ice water was confirmed to be a preferable quenching medium. La(Fe1-xCox)11.9Si1.1(x=0.068) compounds with almost single 1:13 phase were obtained at 1473 K after 15 d. 相似文献
7.
La_(15-x)Nd_xFe_(14)Ni_(64)Mn_5B_2(x=0~6)储氢合金的结构和电化学性能 总被引:1,自引:1,他引:0
采用中频感应熔炼-快淬炉制备了La15-xNdxFe14Ni64Mn5B2(x=0、2、4、6)储氢合金。扫描电镜(SEM)及能谱(EDS)分析表明,这些合金由(La,Nd)Ni5相、(Fe,Ni)相和(La,Nd)3Ni13B2相组成。X射线衍射(XRD)分析表明,Nd含量对合金的相组成没有影响,但随Nd含量的增加,衍射峰向高角度方向轻微位移。电化学测试表明,随x值的增大,合金电极的放电容量及高倍率放电能力(HRD)先增加后减小,x=2时的放电容量(302mAh.g-1)最高,HRD值(1050 mA.g-1放电时为65.6%)最大。充放电循环稳定性随x值的增大而增加。适量的Nd替代La有利于改善LaFeNiMnB储氢合金的综合电化学性能。 相似文献
8.
TheanisotropyfieldHAofPr2 Fe14 Bisabout 30 %higherthanthatofNd2 Fe14 Bwhichresultsinhighin trinsiccoercivityfornanocrystallineexchangecoupledcompositepermanentmagnets .SothePr basedisotropicbondedmagnetshavecurrentlyattractedmuchattentions[1~ 4 ] .Howeverthistypeofpermanentmagnethasnotbeenusedinpractice .Thereexistmagneticinteractionsbetweenadja centgrainseitherinnanocrystallinecompositemagnetsorinanassemblyofsinglehardmagneticphaseofrareearth transitionmetalintermetalliccompounds[5~ 8] … 相似文献
9.
A. Tonejc 《Metallurgical and Materials Transactions B》1971,2(2):437-440
The extension of the solid-solubility limit obtained in Al-Fe alloys up to 4.4 at. pct Fe by rapid quenching from the melt
and the appearance of metastable Al6Fe phase for 4 to 20 wt pct Fe have been reported in the past. Present experiments with isochronal and isothermal annealing
of Al-Fe solid solutions containing 3.6 at. pct Fe have shown that the solutions are very stable at room temperature, and
less stable at 200°C, while at 300°C they decompose very rapidly and a metastable Al6Fe phase appears. This phase is replaced by Al3Fe after annealing for 10 min at 550°C or for 16 hr at 400°C. The Al6Fe phase remains stable for 76 hr at 300°C, while taking more than 670 hr to be replaced by Al3Fe. The author discusses the operation of the “two-piston” quenching apparatus and concludes that the sample thickness cannot
serve as a sufficient criterion for quenching effectiveness. 相似文献
10.
采用X射线衍射、扫描电镜及显微硬度等技术,综合比较和分析了H13模具钢在不同热处理状态下经相同气体渗氮处理后表层的组织结构和硬度。结果表明,经淬火+二次回火和淬火+三次回火的试样渗氮后,渗氮层厚度均达到约0.24 mm,致密化合物层厚度达到10 μm以上,表面硬度HV达到950 (约为HRC 67)。这两种热处理状态下渗层中化合物层均由ε相(Fe2N)、γ′相和Fe3O4构成,扩散层均由α Fe相、ε相(Fe3N)、CrN相和γ′相构成,但各相含量有差别。而淬火态和淬火+一次回火态的渗氮试样未能获得具有足够好综合性能的渗层组织。 相似文献
11.
EfectsofAloyingElementsonMicrostructureandMagneticAnisotropyoftheHDDRPowderofNdFeBAloyGaoJianrong(高建荣),SongXiaoping(宋晓平),Wa... 相似文献
12.
The critical points and time temperature transformation (TTT) curves of Fe‐5%V‐5%W‐5%Mo‐5%Cr‐3%Nb‐2%Co (Fe‐V‐W‐Mo) were measured, and the effects of quenching temperature and cooling modes on the microstructure and performance of Fe‐V‐W‐Mo alloy were investigated. The results showed that the hardness of Fe‐V‐W‐Mo alloy increased until the quenching temperature reached 1025°C and dropped down as the quenching temperature exceeded 1050°C in oil cooling. The hardness obtained in air cooling and spray cooling exhibited a similar tendency as that in oil cooling, but the temperature at which the highest hardness was obtained in these slower cooling processes changed to a higher range. The hot hardness and toughness of Fe‐V‐W‐Mo alloy increased with rising quenching temperature until it reached 1150°C, and from then on the toughness began to drop. The main reasons why the structures and properties of Fe‐V‐W‐Mo alloy obviously change under different quenching conditions are particularly analysed at last. 相似文献
13.
《Acta Metallurgica》1986,34(5):831-837
The theoretical model of glass formation and partial crystallization during rapid solidification of a metallic melt describes the homogeneous nucleation within the undercooled melt as well as the heat transfer into the metallic chill substrate. The calculated maximum thicknesses of amorphous foils at quenching onto a copper substrate increase in the order of alloys FeC, FeB, NiSiB and PdSi. Reducing the foil-substrate heat transfer coefficient, increasing the casting temperature and utilizing a steel substrate cause the attainable amorphous foil thickness to decrease. In foils with a large volume fraction crystallized the cooling process is not monotonous. The minimum density of quenched-in nuclei is situated at the substrate-side surface in amorphous foils and at the surface away from the substrate in crystalline foils. 相似文献
14.
Anexternalelectricfieldiswidelyusedtocontrolthemicrostructureandpropertiesofvariousmaterials ,suchasliquid crystallinepolymers[1,2 ] ,oxideglass es[3~ 5] ,ferroelectricmaterials[6 ,7] .Thesufficientlystrongelectricfieldcaninduceacholesteric to nemat icphasetransformationinliquidcrystallinepolymers .Thephaseseparationkineticsduetotheappliedelec tricfieldwasfirstreportedforoxideglassesbydeVekeyandMajumdar[8] .Subsequently ,Liuetal.systematicallystudiedtheeffectofanelectricfieldonthephasesepara… 相似文献
15.
The coercivity enhancement of ball-milled Nd2Fe14B/α-Fe nanocomposite magnets was investigated. It was found that the coercivity could be enhanced through mixing a small amount of Nd powder with as-milled Fe-rich Nd-Fe-B powders. The annealed samples were investigated by means of X-ray diffraction, scanning electron microscopy and magnetic measurement systems. Under annealing, some of Nd powders promoted the formation of hard magnetic phase Nd2Fe14B. On the other hand, a few of Nd would diffuse into the interface of Nd2Fe14B/α-Fe nanocomposite to compensate for the loss of the interfacial magnetic anisotropy. These two features are all beneficial to the coercivity. 相似文献
16.
17.
18.
W. A. Elliott Master of Science at Lehigh University as a part of the Western Electric Company-Lehigh University Master’s Program F. P. Gagliano G. Krauss 《Metallurgical and Materials Transactions B》1973,4(9):2031-2037
A Nd: glass laser has been used to produce and retain metastable phases which are similar to phases obtained by rapid quenching
(“splat cooling”) techniques. A single laser pulse of 10 msec duration was focused onto the surface of an alloy specimen to
provide a beam intensity of approximately 3.7 × 105 watts per sq cm. A small volume of metal in the relatively large specimen immediately underwent melting. Upon cessation of
the laser pulse, the molten metal solidified very quickly. Extremely rapid cooling was achieved due to the presence of nearly
ideal conditions for conduction cooling. Laser melting of various alloys of the eutectic Ag-Cu system resulted in a complete
series of solid solutions, as verified by X-ray analysis. In addition, the laser melt quenching technique provided a threefold
increase in microhardness of the resolidified metal.
Formerly Western Electric Engineering Research Center, Princeton, N. J. 08540 相似文献
19.
Grain Growth Behavior in Sintered Nd-Fe-B Magnets 总被引:2,自引:0,他引:2
The Nd2Fe14B grain growth behavior in sintered Nd-Fe-B magnets was quantitatively described.The effects of sintering temperature and time,and alloy powder size and its distribution on grain growth process were analyzed.Hence,possible grain growth mechanisms in these magnets were qualitatively discussed.The 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 growth.On 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 coalescence.It 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. 相似文献
20.
Investigation of Coercivity Mechanism for Nd-Fe-B Magnets Prepared by Combination of Strip-Casting with Hydrogen Decrepitation Techniques 总被引:1,自引:1,他引:0
The coercivity mechanism of Nd-Fe-B magnets prepared by combination of strip-casting with hydrogen decrepi-tation techniques was investigated. The microstructure of (Nd0.935Dy0.065)14.5Fe79.4B6.1 magnet was observed. The average grain size is about 6 ~ 12 μm. The magnetizing field dependence of the hardmagnetic properties for the (Nd0.935Dy0.065)14.5 Fe79.4B6.1 and the temperature dependence of the coercivity for the Nd14.5Fe79.4B6.1 were investigated. Results show that the coereivity for magnets prepared by the combination of strip-casting with hydrogen decrepitation techniques is controlled by the nucleation mechanism. 相似文献