Magnetic properties of melt spun mischmetals-Fe-Ti-B nanocomposite ribbons

Magnetic properties and phase evolution of melt spun R9.5Fe(bal.)Ti2B10 (R = MM(A), MM(B), MM(C), Pr, Nd, Ce, and La) nanocomposites have been investigated. Based on the results for the X-ray diffraction and thermal magnetic analysis, only 2:14:1 and alpha-Fe phases appear for R = MM(A) and Pr, and an additional Fe3B phase is present for R = MM(B), MM(C), Nd, and Ce. Besides, the uniform fine grain size of 20-40 nm is almost unchanged for the ribbons with various rare earth elements. Accordingly, magnetic properties of MM9.5Fe(bal.)Ti2B10 nanocomposites are mainly dominated by the composition of Mischmetals or the rare earth elements adopted, and are consistent with the outcome for the combinations of magnetic properties of their corresponding R9.5Fe(bal.)Ti2B10 nanocomposites. In this study, the optimum magnetic properties of B(r) = 9.3 kG, (i)H(c) = 12.1 kOe and (BH)(max) = 18.0 MGOe can be achieved for MM(B)9.5Fe(bal.)Ti2B10 nanocomposites. They not only exhibit comparable magnetic properties to the commercial available powders but also reduce the original material cost effectively.     

Spark plasma sintered Sm(2)Co(17)-FeCo nanocomposite permanent magnets synthesized by high energy ball milling

Nanocomposite Sm(2)Co(17)-5?wt% FeCo magnets were synthesized by high energy ball milling followed by consolidation into bulk shape by the spark plasma sintering technique. The evolution of magnetic properties was systematically investigated in milled powders as well as in spark plasma sintered samples. A high energy product of 10.2?MGOe and the other magnetic properties of M(s) = 107?emu?g(-1), M(r) = 59?emu?g(-1), M(r)/M(s) = 0.55 and H(c) = 6.4?kOe were achieved in a 5?h milled and spark plasma sintered Sm(2)Co(17)-5?wt% FeCo nanocomposite magnet. The spark plasma sintering was carried out at 700?°C for 5?min with a pressure of 70?MPa. The nanocomposite showed a higher Curie temperature of 955?°C for the Sm(2)Co(17) phase in comparison to its bulk Curie temperature for the Sm(2)Co(17) phase (920?°C). This higher Curie temperature can improve the performance of the magnet at higher temperatures.     

Structural and Magnetic Properties of Mechanically Alloyed Nd_(15)Fe_(70)T_(15)N_δ(T=V, Mo) Magnets

Structural and magnetic properties of Nd15Fe70T15Nδ(T=V, Mo) alloys, made by mechanical alloying (MA) followed by heat-treatment and nitriding, have been investigated systematically.Effects of annealing temperature on the structure and magnetic properties of the materials were studied by means of X-ray diffraction, AC susceptibility and high field magnetization measurements. Under pure argon atmosphere, the optimum temperatures for the heat treatment are found to be 75 and 850℃ for Nd15Fe7015Nδ and Nd15Fe70Mo15Nδ respectively. Correspondingly, the following magnetic properties are achieved : (1) Nd15Fe70V15Nδ:Br=0.63 T,,HC=8.01kA/cm (10.1 kOe), (BH )max=50.3 kJ/m3 (6 32 MGOe), (2) Nd15Fe70Mo15Nδ :Br=0.42 T. iHc=5.6 kA/cm (7.4 kOe), (BH )max=26.6 kJ/m3 (3.34 MGOe)     

Effect of dopants on the soft magnetic properties and high frequency characteristics of FeCoBM (M = Ti, Nb, Hf, and Ta) thin films

Effect of dopants on the soft magnetic properties and high frequency characteristics of FeCoBM thin films (M = Ti, Nb, Hf, and Ta) have been studied. For (Fe0.55Co0.45)(100-x)B(x) (x = 5-15) thin films, with the increase of B content, the resistivity was increased because B could decrease the crystallinity of the films. The (Fe0.55Co0.45)90B10 thin film showed the optimum properties, where 4piM(s) = 16.1 kG, H(ce) = 64.2 Oe, H(ch) = 13.5 Oe, H(k) = 310 Oe and p = 338 microomega-cm. To reduce the coercivity of the film, the elements M, including Ti, Nb, Hf, and Ta, were selected to substitute for B in the FeCoB films. It was found that (Fe0.55Co0.45)90B6Ti2Nb2 thin film after annealing at a temperature of 200 degrees C for 30 min showed the optimal properties, where 4piM(s) = 15.8 kG, H(ce) = 4.8 Oe, H(ch) = 3.6 Oe, H(k) = 224 Oe and p = 290 microomega-cm. The theoretically calculated ferromagnetic resonance frequency of the developed films can be higher than 5 GHz.     

Phase evolution and magnetic metals co-substituted studies of La and refractory co-substituted alpha i-Fe/R2Fe14B-type nanocomposites

Phase evolution and magnetic properties of (Nd0.95La0.05)(9.5 similar to 11)Febal.M2B10.5, where M=Cr, Ti, Mb, V, Mo, Zr, Hf, Ta, Mn or W, melt spun ribbons have been investigated. Almost all the alloy ribbons, except for (Nd0.95La0.05)(9.5)Fe78M2B10.5 (M=Mo and Mn), consist merely two magnetic phases, namely alpha-Fe and R2Fe14B, which display a better combination of H-i(c) and magnetic energy product. Remanence (B-r) and coercivity (H-i(c)) values in the range of 8.0 to 9.1 kG and 9.5 to 18.9 kOe, respectively, can be achieved. Among compositions studied, the Ti and W-substitutions were found to be most effective in increasing the Br and H-i(c), respectively. For a fixed refractory metal substitution, namely, M=Cr, Ti or Mb, an increase in the total rare earth concentration resulted in nanocomposites of small grain sizes and a high volume fraction of the R2Fe14B phase, leading to an increase in the magnetic properties.     

Exchange Coupling and Magnetic Behavior of SmCo_(5-x)Sn_x Alloys

Exchange coupling and magnetic properties of SmCo5 alloys containing different amounts of Sn were investigated in sintered magnets.X-ray diffraction analysis revealed the formation of Sm2Co17 and Sm2Co7 phases in SmCo5 matrix.Exchange coupling mechanism was evaluated by switching field distribution,dcdemagnetization and magnetization curves as function of reverse applied field.Energy product of 59.2 kJ/m 3(7.4 MGOe),remanent magnetization to maximum magnetization ratio of 0.97 and remanence coercivity to intrinsic coercivity ratio of 1.75 were achieved for 0.2 at.% Sn.     

Magnetic Properties and Thermal Stability of Pr_(1-x)La_xCo_(5-y)Alloys

Pr1-xLaxCo5-y (x=0, 0.15. 0.25, 0.35,1.0, y=0.5, 0.7, 0.9, 1.0) alloys were investigated. The effect of the variation of x and y on magnetic properties and thermal stability of the alloys were studied. The magnetic properties for the Pr0.85La0.15Co4.3 and Pr0.75La0.25Co4.1 magnets are iHc=368 kA/m, Br=0.91 T, (BH)max=145.6 kJ/m3, αBr=-0.03%/℃ and iHc=568 kA/m,Br=0.8 T, (BH)max=127.2 kJ/m3,αBr,=-0.06%/℃, respectively The phase structures of as-cast alloys and magnets were investigated     

纳米晶复合Nd9.5Fe81-xCoxZr3B6.5永磁材料磁性能的研究

采用熔体快淬及晶化退火工艺制备了Nd9.5Fe81-xCoxZr3B6.5(x=0、2、5、8、10)纳米晶合金条带,研究了Co的添加对快淬合金磁性能和居里温度的影响.结果表明,适量Co元素的添加能够有效降低各相晶粒的尺寸,增强了软、硬磁相晶粒的交换耦合作用,从而提高了合金的磁性能.Co含量为5%(原子分数)的合金,经670℃/4min的晶化处理后所得到的最佳磁性能为`Br=0.90T,jHc=588kA/m,(BH)max=117kJ/m3.     

Magnetic properties and microstructures of mischmetal-FeB-(Al, Ti and Al-Co) permanent magnets

The magnetic characteristics of anisotropic MM-FeB- (Al, Ti and Al-Co) permanent magnets have been investigated by using hot-pressing and die-upsetting process. The best magnetic properties obtained in these studies were H _C = 5.1 kOe, B _r = 5.4 kG with (BH)_max = 5.1 MGOe for hot-pressed MM-FeB-Al-Co magnets and H _C = 3.6 kOe, B _r = 6.7 kG, (BH)_max = 6.8 MGOe for die-upset MM-FeB-Al-Co magnets. Higher squareness of demagnetization curve was obtained in anisotropic die-upset MM-FeB- (Al, Al-Co) magnets. X-ray diffraction and STEM investigations revealed that the higher magnetic properties in die-upset magnets were resulted from alignment of the c-axis along the die-upsetting direction. The magnetic anisotropy of the die-upset magnets and the densification of the hot-pressed magnets were increased by partial substitution of Al and Al-Co for Fe.     

High coercivity in melt-spun SmFe10(Ti,M)2 ribbons (M=V/Cr/Mn/Mo)

Magnetic properties of SmFe₁₀(Ti,M)₂ melt-spun ribbons were studied, where M is V, Cr, Mn, and Mo. The ribbons (M=V/Cr/Mo) quenched at 20 m/s exhibit the high coercivities of 4.2-5.5 kOe. Annealing the ribbons quenched at 40 m/s enhances their coercivities in the range of 5.9-10.0 kOe. In particular, SmFe₁₀ (TiV) and SmFe₁₀(TiCr) ribbons yield coercivities of 10.0 kOe and 7.9 kOe, respectively. This is the highest value among the reported melt-spun ThMn₁₂-type structure ribbons. The importance of Sm atmosphere during annealing in minimizing the Sm evaporation from ribbons is also demonstrated     

Sintered Sm2(Co, Fe,Cu,Zr)17 magnets withlight rare earth substitutions

The effects of partial substitution of light rare earths for Sm in (Sm_1-xR_x)₂ (Co,Fe,Cu,Zr)₁₇ have been investigated where R=Ce, Pr, Nd, Pr_0.5Nd _0.5, Ce_0.2Pr_0.4Nd_0.4 and x=0-0.5. Experiments show that both remanence and maximum energy product are improved for x=0.1-0.2, depending upon compositions and heat treatments. For a composition Sm_0.8R_0.2(Co_0.633Fe_0.286 Cu_0.061Zr_0.020)_7.59 with R =Ce_0.2Pr_0.4Nd_0.4, the authors obtained B_r=11.57 kG, _MH_c =15.5 kOe, _BH_c=10.33 kOe, H_k=10.03 kOe, and (BH)_max=30 MGOe     

HDD法制备各向异性NdFeB磁粉的研究

本文探讨了用吸氢—歧化—脱氢(HDD)工艺制取各向异性NdFeB永磁粉末的可能性。研究了成份、氢处理工艺以及后处理等对各向异性现象的影响。研究结果表明,在Nd_xFe_(87)-x-yCo_6B_7Zr_y的合金中经适当的氢气处理,初步获得了各向异性磁粉,由M115型振动样品磁强计所测磁粉的磁性能为:B_r=0.92emu/gm,iH_c=720kA/m(9kOe),(BH)_(max)=112kJ/m~3(14MGOe)。由该粉与3％(重量百分比)的环氧树脂混合制成的各向异性粘结磁体的磁性能为B_r=0.65T,iH_c=744kA/m(9.3kOe),(BH)_(max)=64k3/m~3(8MGOe)。本文还观察了各向异性粉的微观结构。     

Effect of the current annealing (without and with tensile stress) on the soft magnetic behaviour of Fe73.5-x(Co0.5Ni0.5)xSi13.5B9Nb3Cu1 alloy ribbons (x = 2.5, 5 and 10)

Experimental data on microstructural (crystalline volume fraction, grain size) and magnetic (coercive field) properties in amorphous and nanocrystalline Fe73.5-x(Co0.5Ni0.5)xSi13.5B9Nb3Cu1 alloy ribbons (x = 2.5, 5 and 10) are presented. Nanocrystalline structure was developed by annealing the precursor amorphous ribbons by current annealing (CA) and stress-current-annealing (SA). Microstructural analysis of the treated ribbons using X-ray Diffraction showed a high content of amorphous phase in the bulk. In addition, substantial changes in the crystalline state such as grain size of the samples annealed at different conditions were observed. The alloy composition also affects greatly the grain size,: increasing the (Co,Ni) content leads to higher values of the average grain size. The evolutions of the coercive field with the two kinds of thermal treatment were analysed, allowing us to conclude that the addition of (Co,Ni) tends to reduce the magnetic softness character of the original material, while the treated SA samples show higher coercivities higher than those treated without by CA.     

Magnetic properties of a mischmetal-cobalt alloy

The magnetic properties of a mischmetal-cobalt alloy are studied. A mischmetal-64% cobalt alloy was melted in induction furnace under a protective atmosphere of argon. The melt was solidified in a magnetic field of 7 kOe, and cooled to a temperature of 950° C and was thereafter quenched in water. Specimens of suitable dimensions were machined, heat-treated in the temperature range 1000–1100° C for various lengths of time and the magnetic properties evaluated. The (BH)_max value was 10·3 MGOe which was associated with aB _r value of 7 kG and H_c value of 5 kOe. The results obtained offer feasibility to design new MM-Co₅ magnets through developments in processing technique.     

Phase Evolution and Magnetic Studies of La and Refractory Metals Co-substituted α-Fe/R_2Fe_(14)B-type Nanocomposites

1. IntroductionIn last decade, two types of NdFeB nanocomposite powders, namely, or-Fe/Nd,Fe,.B['] andFe,B/Nd,Fe,.B['] t have drawn much attention of theresearcher for the bonded magnet application, because of their high remanence (B.) and high maximum energy product ((BH)...). The deficiency ofthese types of nanocomposites is their lower coercivity (tHe <8 hoe) arisen from the existence of certain amount of magnetically soft or-Fe or Fe3B phases,which might limit their application in h…     

The (SmZr)Co$_3$Phase in Sm(CoFeCuZr)$_rm z$Magnets

Detailed microstructural characterization of magnets and homogenized as-cast alloys, which included X-ray diffraction Rietveld analysis, has indicated that the so-called platelet or lamellae phase is (SmZr)₁(CoFeCu)₃ with the PuNi₃ structure and lattice parameters a~0.5 nm and c~2.4 nm. The structural and magnetic properties of the (SmZr)Co₃ phase were investigated. The microstructure shows two phases differing in their Zr/Sm ratio. Magnetization curves for the samples (Sm_0.33Zr _0.67)Co₃, (Sm_0.33Zr_0.67)Co _2.97Fe_0.03, and (Sm_0.67Zr_0.33)Co₃ are consistent with the two-phase microstructure observed. Room temperature coercivity values of these samples are low (ap1 kOe.)     

Fabrication and magnetic property of BaSm(x)Fe(12-x)O19 (x < or = 0.4) nanofibers

BaSm(x)Fe(12-x)O19 (x < or = 0.4) ferrite nanofibers were prepared by sol-gel method from starting reagents of metal salts and citric acid. These nanofibers were characterized by TG-DTA, FTIR, SEM, XRD and VSM. These results show that the BaSm(x)Fe(12-x)O19 (x < or = 0.4) ferrite nanofibers were obtained subsequently from calcination at 750 degrees C for 1 h. The BaSm(x)Fe(12-x)O19 (x < or = 0.4) microstructure and magnetic property are mainly influenced by chemical composition and heat-treatment temperature. The grain sizes of BaSm0.3Fe11.7O19 ferrite nanofibers are in a nanoscale from 40 nm to 62 nm corresponding to the calcination temperature from 750 degrees C to 1050 derees C. The saturation magnetization of BaSm(x)Fe(12-x)O19 ferrite nanofiber calcined at 950 degrees C for 1 h initially decreases with the Sm content from 0 to 0.3 and then increases with a further Sm content, while the coercivity exhibits a continuous increase from 348 kA x m(-1) (x = 0) to 427 kA x m(-1) (x = 0.4). The differences of magnetic properties are attributed to lattice distortion and enhancement for the anisotropy energy.     

Structure and Magnetic Properties of Nd-Fe-B/a-Fe Nanocomposite Magnets by Co, Nb, Dy Substitutions

Structure and magnetic properties of the nanocomposite magnets prepared by mechanical alloying procedure with composition 55 wt pct Nd (Fe0.92B0.08)5.5+45 wt pct a-Fe, 55 wt pct Nd(Fe0.8-xCo0.12Nbx B0.08)5.5+45 wt pct a-Fe (x=0.00, 0.01, 0.03) and 55 wt pct (Nd0.9Dy0.1) (Fe0.77Co0.12Nb0.03B0.08)5.5+45 wt pct a-Fe were studied. It was found that substitution of Co for Fe could significantly improve the permanent magnetic properties of the nanocomposite magnets and typically, the maximum magnetic energy product was increased from 104.8 kJ/m3 (13.1 MGOe) to 141.6 kJ/m3 (17.7 MGOe). In contrast to the case of conventional nominally single-phase magnets, the addition of Nb results in promoting the growth of a-Fe grain and is thus unfavorable for the improvement of permanent magnetic properties of the nanocomposites. Although the addition of Dy can increase the coercivity of the magnets, the increase of magnetic anisotropy of hard phase leads to decrease of the critical grain size of soft phase. Additionally it causes the difficulty of preparing the nanocomposites because it is more difficult to control the grain size of soft phase to meet the requirement of appropriate exchange coupling between hard and soft grains.     

Machinable REPM with Excellent Intrinsic Coercive ForcePrepared by DS Technology

To obtain excellent magnetic properties of machinable REPM prepared by directional solidification (DS) technology Space A, a composition area with θ=0°~5° where easy axis is parallel to solidified direction of alloys, has been established in Zr-Sm-La-Co-Cu-Fe system. In 2/17+1/5+Co, and 2/17+1/5 region near Co phase of Space A, one obtains:Vf = 80.933 - 2.739Zr - 1.828Sm - 0.773Co - 0.147Cu + 0.415Fe + 0.218LaNonequilibrium solidification process of alloys in 2/17+1/5+Co region, is as follows: L→Co,L→2/17, L+2/17→1/5 and L→1/(5-x)+1/(5+x). The product of partially completed peritectic reaction, and 1/(5-x) and 1/(5+x) phases can all be transformed into a homogeneous 1/5 phase after solution treatment in 1413 K for 5 h. Containing 3~6% Co phase magnetically hardened by 0.5~2.5% V, the DS magnets have been achieved with both improved toughness and excellent coercive force of 520 kA/m.     

Anisotropic NdFeB Magnet Fabricated by Single Stroke Hot Deformation

1. IntroductionHard magnetic properties of the materials, such ascoercivity (He), remanence (B,), and energy product[(BH)...] depend strongly on the composition andthe processing conditionslll. The optimally quenchedmelt-spun ribbons of NdFeB alloys produced by rapidqllenching process have equiaxed and randomly oriellted NdZFe14B grains. In order to obtain anisotropicNdFeB grains, the general method is followed by hotpressing and die-upsetting of the ribbon powder oneafter anotherll'2]. …