Effect of Multiple Alloying Elements on Microstructure and Magnetic Properties of Nanocomposite Nd2Fe14B／α-Fe Magnets

TheappearanceofnanocompositemagnetsbroketheremanencelimitpredictedbyStoner Wolhfarthmodethattheremanenceofisotropicmagnetwouldnotexceedhalfofitssaturationmagnetization[1] .Accord ingtoSkomski′scalculation[2 ] ,highmaximalenergyproduct (BH) maxof 80 0kJ·m-3 couldbeachievedinNd2 Fe14 B α FenanocompositewhentheaveragegrainsizeofNd2 Fe14 Bisrefinedtoabout 2 0nmandthatofα Fetoabout 10nm ,becauseoftheeffectofrema nenceenhancement (Mr Ms >0 .5 ) .Unfortunately ,thereported (BH) max(185kJ·…     

Texture of Nanocomposite Nd2Fe14B/α-Fe Melt Spun Ribbons

Highly textured nanocomposite Nd9Fe84.5Nb0.5B6 ribbons were obtained by rapid solidification at wheel speeds from 15 to 20 m·s-1.X-ray diffraction(XRD)shows that these ribbons are preferentially orientated with the c axis of Nd2Fe14B phase perpendicular to the surface of the ribbons.The texture of Nd2Fe14B phase on the free surface is stronger than that on the contact surface and decreases with increase of wheel speed.The texture of Nd2Fe14B phase seems to be caused by the preferential growth of the crystal nuclei favorable orientation with their c-axes along the temperature gradient during rapid solidification,which can be explained by a growth circular cone(GCC).The intensity of the anisotropy can be expressed by the magnitude of the cone generating angle.The supercooling velocity and wheel speed will influence the cone generating angle,which in turn influences the anisotropy.The remanence and maximum energy product in the direction perpendicular to the ribbon surface is much higher than that in the direction parallel with the ribbon surface.High remanence and maximum energy product can be obtained in the direction perpendicular to the ribbon surface.The texture of Nd2Fe14B phase decreases gradually after annealing above 600 ℃,which is mainly attributed to the precipitation of new α-Fe from Nd2Fe14B phase with super-saturated Fe.Decreasing the annealing temperature or reducing the annealing time is beneficial for preserving the anisotropy of Nd2Fe14B phase after annealing.     

A Study of Two-Phase Nanocrystalline Nd_(8.5)Fe_(75)Co_5Cu_1Zr_3Nb_1B_(6.5)Permanent Magnet

Materialswithenhancedremanentmagneticpo larizationwereinitiallypreparedbyCoehoorn[1] frommelt spunNd3.8Fe77B19.2 ribbonsbyheattreatment .Thesimilarbehaviorwasalsoobservedfrommelt spuntwo phasesamplesofNd2 Fe14 Bandα Fe[2 ] .Themag neticpropertiesofisotropicnanocrystallinetwo phasepermanentsdependsensitivelyonmicrostructuralfea tures,suchasdistributionofmagneticallyhardandsoftphases ,meangrainsize ,particleshapeandgrainboundarytype[3] .Inordertoobtainhighmaximumenergyproduct ,itisnecessaryt…     

Evolution of crystallographic alignment in Tb-Fe-B melt-spun ribbons

Ternary Tb-Fe-B ribbons were prepared via melt-spun technique under different wheel speeds of 5-25 m/s.Effect of wheel speed on the crystal structure and microstructure of the ribbons was investigated.All the ribbons quenched under different wheel speeds crystallized in single Tb2Fe14B phase with tetragon structure.Different crystallographic alignment evolutions were observed in the free side surface and wheel side surface of the ribbons.On the free-side surface,an in-plane c-axis crystal texture of Tb2Fe14B phase was found in the ribbons quenched at 5 m/s.However,with the increase in the wheel speed,the direction of the c-axis texture turns to perpendicular to the ribbon surface.On the wheel-side surface,a strong c-axis texture perpendicular to the ribbon surface was observed in the ribbons quenched at 5 m/s,and then weakened gradually with the increase in the wheel speed.Further investigation showed that the competition of the two types of temperature gradients during the quench process was responsible for the crystallographic alignment evolution in the ribbons.     

Influence of Zr Additions on Microstructure and Magnetic Properties of Nanocomposite Nd10.5Fe78-xCo5ZrxB6.5 (x=0～5) Alloys

The influence of Zr addition on the microstructure and magnetic properties of nanocomposite Nd10.5Fe78-xCo5ZrxB6.5 (x=0～5) alloys was investigated. It was found that the intrinsic coercivity could be significantly improved by the addition of 2% (atom fraction) Zr. The presence of small amount of amorphous phase is responsible for the low intrinsic coercivity for Zr-free alloy. The small amount addition of Zr may suppress the growth of grains of α-Fe and Nd2Fe14B phases. The more homogeneous microstructure with an average grain size of 20 nm can be obtained for Nd10.5Fe76Co5Zr2B6.5 alloy.     

双相纳米晶Nd2Fe14B/α-Fe磁体的热稳定性研究

采用快淬法制备出成分为Nd8.5Fe75Co5Cu1 Zr3Nb1 B6 .5和Nd8.5Fe74 Co5Cu1 Nb1 Zr3Cr1 B6 .5的双相纳米晶永磁材料 ,加入粘结剂后制成粘结磁体 ,研究了其磁性的热稳定性和抗氧化性能。结果发现 ,两种双相纳米晶磁体都具有较好的抗氧化性能 ,且在一定温度处理后磁通损耗较少 ,其中加入合金元素Cr后效果尤为明显。     

Crystallographic alignment and magnetic anisotropy in melt-spun Nd-Fe-B/α-Fe composite ribbons with different neodymium contents

Crystallographic alignment and magnetic anisotropy were studied for NdxFe94-xB6 (x=8,9,10,11) ribbons prepared via melt-spinning. Effect of Nd content and wheel speed on the crystal structure and magnetic properties of the ribbons was investigated. Both the free and wheel side of the ribbons could obtain strong c-axis crystal texture of Nd2Fe14B phase perpendicular to the ribbons surface at low wheel speed,but the texture weakened gradually with the increase of the wheel speed. Increase of Nd content led to better formation of crystal texture in the ribbons,indicating that the α-Fe phase might undermine the formation of crystal texture. Magnetic measurement results showed that the magnetic anisotropy of the ribbons exhibited corresponding behavior with the invariance of the c-axis crystal texture of Nd2Fe14B phase in the ribbons,and the coercivity of the ribbons rose with the increase of both Nd content and wheel speed during melt-spun process.     

Effect of super heat treatment on crystallization behavior and magnetic properties of Nd4.5Fe77B18.5 nanocomposites

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...     

Fe81Zr5Nb4B10非晶合金的晶化过程及其磁性研究

采用单辊快淬法制备Fe81Zr5Nb4B10非晶合金带,并在不同温度下对其进行退火处理,利用XRD和振动样品磁强计(VSM)测试了合金自由面和贴辊面的结构及磁性能。结果表明:随着退火温度的增加,淬态合金由完全的非晶态结构转变为非晶与纳米晶的混合结构,晶粒尺寸、晶化体积分数增大,晶粒间的非晶层厚度减小。和自由面相比,贴辊面的晶粒尺寸较大,晶化体积分数较小,晶粒间的非晶层厚度较大。合金的矫顽力和比饱和磁化强度σs随着退火温度的升高逐渐增大。     

Magnetic Properties of B-Rich Nano-Composite REyTM 90-y-xNbxB10 Alloys

We report and discuss the results of a study of the structures and magnetic properties of B-rich (10 at%) nanocomposite alloys, based on the formula RE_yTM_90-y-x Nb_xB₁₀ (RE=Nd, Nd+Pr, TM=Fe, Fe+Co; y=8,10,12, x=0,2,4) and processed by devitrification of melt-spun amorphous precursors. Considerable enhancement of the intrinsic coercivity, together with good to excellent remanence and energy density values were observed for Co-containing compositions with y =10 and x =2,4. The intrinsic coercivity and remanence enhancements are ascribed to the grain refining effects of Nb, particularly with respect to the soft magnetic phases, and thus to more complete exchange coupling of the soft grains to the hard phase grains than for the Nb-free alloy.     

Giant Magnetoimpedance Effect in Fe89Zr7-xHfxB4 Ribbon

The giant magnetoimpedance (GMI) effect in Fe89Zr7-xHfxB4 (x=0.5 or 1.0) ribbon annealed at different temperatures was investigated. The results show that some addition of hafnium to Fe-Zr-B raises the GMI effect. There is an optimum annealing temperature about 570℃ for obtaining large GMI behavior in Fe89 Zr7-xHfxB4 (x=0.5 or 1.0) nanocrystalline ribbons. At 900 kHz, the magnetoimpedance for Fe89 Zr6Hf1B4 nanocrystalline ribbon monotonically changes with applied DC field, and reaches-33.4 % at 7 162 A/m. Meanwhile, the results show that the transverse anisotropy field of Fe89 Zr6 Hf1 B4 ribbons decreases with increasing annealing temperature from 520℃ to 620℃.     

Computer Simulation of Effect of Intergrain Exchange Interaction on Magnetic Properties of Nanocomposite Magnets

Nanocompositemagnetsareoneofcandidatesformagnetsinthenextgeneration .Inananocompositemagnet,theexistenceofmagneticallysoftgrainswithahighsaturationmagnetizationenhancestherema nence,andconsequentlyahigh (BH ) max valueisachieved[1] .Asthemagnetizationinthesoftgrainsispreventedfromtheirreversalbytheintergrainex changeinteractionbetweensoftandhardgrains ,theintergrainexchangeinteractionplaysanimportantroleindeterminingmagneticproperties .Therefore ,itscontrolisconsideredtobeakeytechnologyforobt…     

Evolution of crystallographic alignment in Tb-Fe-B melt-spun ribbons

Ternary Tb-Fe-B ribbons were prepared via melt-spun technique under different wheel speeds of 5-25 m/s. Effect of wheel speed on the crystal structure and microstructure of the ribbons was investigated. All the ribbons quenched under different wheel speeds crystallized in single Tb₂Fe₁₄B phase with tetragon structure. Different crystallographic alignment evolutions were observed in the free side surface and wheel side surface of the ribbons. On the free-side surface, an in-plane c-axis crystal texture of Tb₂Fe₁₄B phase was found in the ribbons quenched at 5 m/s. However, with the increase in the wheel speed, the direction of the c-axis texture turns to perpendicular to the ribbon surface. On the wheel-side surface, a strong c-axis texture perpendicular to the ribbon surface was observed in the ribbons quenched at 5 m/s, and then weakened gradually with the increase in the wheel speed. Further investigation showed that the competition of the two types of temperature gradients during the quench process was responsible for the crystallographic alignment evolution in the ribbons.     

Microstructural Evolution in Nd2Fe14B/α-Fe Bearing Zr-Nb Nanocomposite Magnet

Microstructural evolution in Nd₂Fe₁₄B/α-Fe bearing Zr-Nb nanocomposite magnet has been investigated. The magnetic properties, especially the coercivity were enhanced with the addition of Zr and Nb elements for the fine and uniform microstructure. The results of three-dimensional atom probe (3DAP) revealed that (Zr,Nb)Fe₂ intergranular phase existed at the boundary of grains, suppressing the grain growth during crystallization process. The interaction coupling between grains was enhanced and the magnetic properties were improved for the refinement of grains.     

Effects of Magnetic Annealing on Magnetic Properties in Nd4Fe76Co3(Hf1-xGax)B16 Alloy

Ｒｅｃｅｎｔｌｙ,ｎａｎｏｃｒｙｓｔａｌｉｎｅｔｗｏ－ｐｈａｓｅｍａｇｎｅｔｓｈａｖｅｂｅｅｎａｔｒａｖｔｅｄｅｘｔｅｎｓｉｖｅｌｙｄｕｅｔｏｉｔｓｕｎｕｓｕａｌｙｈｉｇｈｉｓｏｔｒｏｐｉｃｒｅｍａｎｅｎｃｅｒａｔｉｏ,ｒｅｌａｔｉｖｅｌｙｈｉｇｈｃ...     

Effects of magnetic annealing on crystallization and magnetic properties of Nd2Fe14B/α-Fe nanocomposite magnets

Crystallization and magnetic properties of Nd2Fe14B/α-Fe nanocomposite magnets have been investigated by annealing the as-spun ribbons with magnetic field.The crystallization process was accelerated by field annealing.The hysteresis loop became to be fat by magnetic annealing at 645 oC for 4 min,which was 690 oC for ribbons annealing without magnetic field.The relative content of α-Fe phase was increased from the results of XRD.The strength of the magnetic field had no obvious influence on the remanence and coercivity,but modified the squareness of hysteresis loop.     

Effect of yttrium substitution on magnetic properties and microstructure of Nd-Y-Fe-B nanocomposite magnets

The phase evolution,microstructure and magnetic properties of Nd9-xYxFe72Ti2Zr2B15(x=0,0.5,1,2) nanocomposite ribbons were investigated.It was found that substitution of Y enhanced glass forming ability of the over-quenched ribbons and stabilized the amorphous phase during post annealing treatment.Appropriate content of Y substitution effectively refined the microstructure and enhanced the remanence of the annealed samples.The residual amorphous intergranular phase in the annealed sample improved the square...     

Coercivity enhancement of Nd2Fe14B/α-Fe nanocomposite magnets through neodymium diffusion under annealing

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.     

Effects of Alloying Elements on Microstructure and Magnetic Anisotropy of the HDDR Powder ofNd-Fe-B Alloy

ＥｆｅｃｔｓｏｆＡｌｏｙｉｎｇＥｌｅｍｅｎｔｓｏｎＭｉｃｒｏｓｔｒｕｃｔｕｒｅａｎｄＭａｇｎｅｔｉｃＡｎｉｓｏｔｒｏｐｙｏｆｔｈｅＨＤＤＲＰｏｗｄｅｒｏｆＮｄＦｅＢＡｌｏｙＧａｏＪｉａｎｒｏｎｇ（高建荣），ＳｏｎｇＸｉａｏｐｉｎｇ（宋晓平），Ｗａ...     

快凝Nd-Fe-B厚带的制备与组织结构

采用单辊快凝法取代传统的铸锭法制备出了厚度为0.1～0.4mm的NdFeB厚带.通过对制备快凝厚带过程中不同的工艺参数的探索,获得了工艺参数、带片厚度及显微组织间的关系.结果表明:制备0.25～0.35mm厚带的最佳工艺参数为:辊轮转速在10m/s左右,喷射压力0.08～0.10MPa,辊嘴间距(2±0.5)mm.当带片厚度为0.3mm时,带片中以Nd₂Fe₁₄B相为主,沿着(410)方向Nd₂Fe₁₄B含量比例较大;其显微结构主要是Nd₂Fe₁₄B片状晶,富Nd薄层相之间的间距约为5 μm.带片厚度为0.4mm时,厚带试样中α-Fe含量明显大于Nd₂Fe₁₄B含量,并且择优取向变成了(008).厚度0.1mm的厚带的显微结构中是细小的急冷等轴晶,厚度0.4mm的厚带中有较大区域的等轴晶.