Fe-Nd-Al系非晶合金条带的磁性机理

对Fe_(53)Nd_(37)Al_(10)合金甩带速度为40和20 m/s条带样品的磁性能、磁粘滞行为和微观结构进行研究,分析了该合金条带的矫顽力机理。结果表明:Fe_(53)Nd_(37)Al_(10)合金甩带速度为40和20 m/s条带样品的剩余磁化强度M_r分别为33.50和36.05(A·m~2)·kg~(-1),矫顽力_iH_c为62.00和121.50 kA/m。40 m/s条带样品的热涨落场H_f,激活体积V_a和激活直径D_a分别为2.47 m T,3.90×10~(-18)cm~3和19.53nm;而20 m/s条带样品为2.73 mT,3.53×10~(-18)cm~3和18.89 nm。40 m/s条带样品里面存在直径小于5 nm的纳米团簇,而20 m/s条带样品的纳米团簇直径为5~10 nm,且纳米团簇数量更多。Fe-NdAl非晶条带里面同时存在交换耦合和钉扎2种作用,纳米团簇的尺寸和数量,以及多个团簇组成的作用单元是影响非晶条带矫顽力的主要原因。     

Nd60Fe30M10（M=Al，Si，Ga）系非晶永磁的性能与组织结构

采用真空快淬设备以辊速5m／s、10m／s、15m／s、20m／s、30m／s制备了Nd60Fe30M10（M=Al,Si,Ga）系的“非晶带”,研究了制备速度对“非晶带”永磁性能和结构的影响。实验结果表明：Nd60Fe30Si10和Nd60Fe30Ga10同经典合金Nd40Fe30Al10一样,也显示出非晶永磁性能,并且比相同条件下制备的Nd60Fe30Al10“非晶带”的永磁性能更好;三种“非晶带”的矫顽力随辊速的降低而提高。对Nd60Fe30Al10“非晶带”的TEM分析表明,以30m／s辊速制备的“非晶带”,有2～5nm的析出物弥散分布在非晶基体上;而以5m／s辊速制备的“非晶带”,有10nm左右和150-200nm的析出物分布在非晶基体上。析出物的生成,促进了矫顽力的提高。     

Nd60-xPrxFe30Al10 (x=0, 9, 15)大块非晶合金的磁粘滞性研究

对Nd60-xPrxFe30Al10(x=0,9,15,at%)大块非晶合金的磁粘滞行为进行了研究,进而分析了该类合金的矫顽力产生机理。结果表明:Nd60-xPrxFe30Al10(x=0,9,15)合金在室温均表现为硬磁性,随着Pr元素含量的增加,合金的内禀矫顽力iHc逐渐减小。在合金的不可逆磁化率χirr随外磁场变化的曲线中,均在各自的内禀矫顽力附近出现了明显的峰。Pr元素部分替换Nd元素后,基本不影响合金的磁粘滞变化趋势。当Pr元素含量从0at%增加到15at%时,合金的热涨落场Hf略有减小,从11.1mT减小到9.9mT;激活体积Va由2.6×10-18cm3增加到2.9×10-18cm3;激活直径Da由17.1nm增加到17.7nm。激活直径Da的值与Nd基大块非晶里的纳米晶团簇(cluster)的尺寸相当,这可能是该类合金具有明显硬磁性的原因之一。     

NdYFeAl合金的非晶形成能力与磁性

采用铜模铸造方法研究了Nd70-x Fe20Al10Y，(x=0，5，10，15)合金的非晶形成能力。Nd70Fe20A10和Nd60Fe20Al10Y10具有较大的非晶形成能力，在普通铜模铸造条件下，至少可以制备出直径为3mm的块状非晶。随合金元素Y的增加，合金的热稳定性提高，在x=15％(原子分数，下同)时，合金Nd55Fe20Al10Y15表现出明显的玻璃转变现象，玻璃转变温度瓦、晶化温度Tx和过冷液相区△Tx分别为777K，830K和53K。Y的加入对Nd70-xFe20Al10Yx块状非晶合金的硬磁性能影响很大，矫顽力(Hc)随Y的加入单调减少，在Y=15％时表现为软磁特征。还讨论了影响非晶形成能力和磁性等因素。     

Nd60Fe20Al10-xCo10Bx非晶合金的结构、磁性能和晶化行为的研究

采用示差扫描量热法(DSC)，X射线衍射(XRD)和振动样品磁强计(VSM)研究了Nd60Fe20Al10-xCo10Bx(x=0，2，5)大块非晶合金的结构、磁性能和晶化行为。结果表明：Nd60Fe20Al10-xCo10Bx非晶合金在晶化前既没有发生玻璃转变也没有过冷液相区；Nd60Fe20Al10Co10合金的DSC曲线上在360℃～475℃之间有1个宽的放热峰，加入2at％～5at％的B后该放热峰消失。铸态Nd60Fe20Al10-xCo10Bx(x=0，2，5)大块非晶合金在室温具有硬磁性。随B含量的增加，合金的内禀矫顽力显著增加，而饱和磁化强度和剩磁则有所下降。B的加入使Nd60Fe20Al10Co10合金的晶化行为发生明显变化。     

辊速及晶化工艺对(Nd, Pr)13Fe80Nb1B6快淬薄带组织和矫顽力的影响

用熔体快淬法制备(Nd,Pr)_(13)Fe_(80)Nb_1B_6快淬薄带并晶化处理,研究辊速和晶化条件对其组织和矫顽力的影响.结果表明,在10～20、25和35 m/s分别得到纳米晶、部分非晶和完全非晶薄带,且在18 m/s制备的薄带有较好的c轴各向异性.快淬态薄带的矫顽力随辊速(10～25 m/s)的增大而增加.非晶薄带晶化后由(Nd,Pr)_2Fe_(14)B相和富稀土相组成,且完全非晶薄带晶化后比部分非晶薄带晶化后的矫顽力要高,这是由于前者比后者具有更均匀的微结构造成的.非晶薄带晶化后矫顽力最大为1616 kA/m,高的矫顽力与添加Pr和Nb有关.     

Nd含量对纳米晶Nd_xFe_(94-x)B_6合金磁性能的影响

用X射线衍射(XRD)、差示扫描量热分析(DSC)、高分辨扫描电镜(HRSEM)和振动样品磁强计(VSM)等研究了Nd含量对快淬纳米晶NdxFe94-xB6(x=11.0-16.8)合金的组织结构、磁性能、交换耦合作用和矫顽力的影响.结果表明,22 m/s(甩带速度)快淬带在最佳退火条件下,合金带的内禀矫顽力Hci由x=11.0的601.. kA/m单调升高到x=16.8的1277.3 kA/m;相反,剩余磁极化强度Jr由x=11.0的1.047 T单调下降到x=16.8的0.721 T,最大磁能积(BH)max随Nd含量增加先升高后下降Nd11.8Fe82.2B6金带的综合性能最好:Jr=0.992 T,Hci=727.9 kA/m,(BH)max=137.2 kJ/m3.Nd2Fe14B晶粒之间的交换耦合作用随Nd含量增加而降低,但x=16.8的合金带仍具有较强的交换耦合作用.矫顽力主要由钉扎场决定.最佳退火后,合金薄带的晶粒尺寸随Nd含量增加无明显变化.针对不同Nd含量的合金,建立了一个组织模型,利用该模型很好地解释了Nd含量对磁性能及交换耦合作用的影响机制.     

基于团簇+连接原子模型的Fe-B-Si-Ta块体非晶合金的成分设计

依据团簇+连接原子模型设计具有高玻璃形成能力的Fe-B-Si-Ta软磁块体非晶合金,以共晶点Fe83B17对应的共晶相Fe2B为基础,根据最大径向原子数密度和孤立度原则,得到以B为心的[B-B2Fe8]主团簇,结合理想非晶合金团簇式的电子浓度判据,构建出Fe-B二元非晶合金的理想团簇式[B-B2Fe8]Fe.为提升Fe-B二元合金的非晶形成能力,选择与Fe具有较大负混合焓的Si替代[B-B2Fe8]团簇的中心原子B,得到Fe-B-Si三元非晶合金的理想团簇式[Si-B2Fe8]Fe.由于Ta与B和Si间具有较大的负混合焓,进一步以Ta替代[Si-B2Fe8]Fe团簇式中壳层位置的Fe原子,设计出[Si-B2Fe8-xTax]Fe四元非晶系列成分.结果表明,[Si-B2Fe8-xTax]Fe在x=0.4~0.7成分处均可形成直径为1.0 mm的非晶合金棒.其中,[Si-B2Fe7.4Ta0.6]Fe合金的非晶形成能力最佳,其非晶样品的约化玻璃转变温度Trg为0.584,玻璃转变温度Tg为856 K,过冷液相区宽度ΔTx达33 K.[Si-B2Fe8-xTax]Fe(x=0.4~0.7)块体非晶合金的Vickers硬度Hv随Ta的添加从1117 HV(x=0.4)上升到1154 HV(x=0.7).[Si-B2Fe7.6Ta0.4]Fe非晶合金具有良好的室温软磁性能,其饱和磁化强度Bs为1.37 T,矫顽力Hc为3.0 A/m.     

Nd60Fe30Al10大块非晶的制备及其热稳定性

采用熔渣包覆水淬法获得了直径为6mm,长度为50mm的非晶Nd60Fe30Al10合金,并对其非晶形成能力进行了研究。在三元系非晶合金中,除Pd基合金外,这是目前所报道的采用水淬法能获得的最大尺寸的非晶合金。对Nd60Fe30Al10在同样的条件下可获得直径为3mm,长度为50mm的部分非晶组织。与普通铜模铸造方法所获得的临界直径相比,前者提高了2mm,而后者降低了4mm.利用DTA和DSC对Nd60Fe30Al10合金的热熔点和形成能力进行了分析,所计算的临界冷却速率为0.55K／s,表明该合金具有较大的非晶形成能力。表观晶化能计算结果和DSC曲线分析表明,Nd60Fe30Al10非晶的热稳定性较低。     

纳米晶复合Nd10Fe80-xNbxB10(x=0~6)永磁合金的磁性能

采用熔体快淬法制备成分为Nd10Fe80-xNbxB10(x=0～6)的非晶条带,退火处理后得到纳米晶复合永磁合金。利用振动样品磁强计(VSM)分析该合金系的磁性能和软、硬磁性相间的交换耦合作用。结果表明,适量的Nb元素的添加可以使软、硬磁性相的晶粒细化,从而有效地增强合金中软、硬磁性相间的交换耦合作用,进而提高合金的综合磁性能。当Nb含量为4at%时,制得的合金条带具有最佳的综合磁性能:Hcj=936.02kA/m,Br=0.91T,(BH)max=125.86kJ/m3。     

Effects of quenching speed and Joule heating on the magnetic properties of Nd9Fe86B5 ribbons

1 IntroductionNanocomposite two-phase magnets are an im-portant type of permanent magnetic materials that have attracted much attention in recent years. Com-bining the high coercive force of the hard magnetic phase and the large saturation magnetization o…     

Magnetic property and recording performance of chemical deposition CoP thin films

The thickness of CoP thin films prepared by wet chemical deposition is of crucial importance on magnetic property and recording perform-ance. The coercivity of CoP films decreased with increasing film thickness. The coercivity was 45.37 kA m 1 at the thickness of 300 nm, and decreased to 21.65 kA m 1 at 5.7 μm. Recording performance tests indicate that, for drums with the same size, different recorded magnetic pole density have different thickness requirements. For 40 mm diameter magnetic drum, the optimal ...     

RE2Fe14B/α-Fe(RE=Nd,Dy,Pr)纳米复合永磁材料的研究

随着稀土含量的增加,快淬薄带矫顽力提高,剩磁降低,当稀土总量为10at%和快淬速度为12 m/s时,快淬薄带的矫顽力可达955 kA/m.当稀土总量为9.5at%时,快淬薄带晶化后的磁性能几乎不受快淬速度的影响.Dy替代部分Nd,提高了快淬薄带的非晶形成能力和热稳定性;经过晶化处理后,快淬薄带的矫顽力明显提高,剩磁略有下降,居里温度提高.Pr替代部分Nd,也提高了快淬薄带的非晶形成能力和热稳定性:经过晶化处理后,快淬薄带的剩磁和矫顽力都有所增加.     

放电等离子烧结Fe3B／（Pr,Tb）2Fe14B块体纳米晶双相复合永磁体的性能

采用放电等离子烧结技术将非晶Pr4.2Tb0.3Fe78B17.5薄带制备成块状纳米晶复合磁体。研究了烧结条件对磁体密度、微观结构和磁性能的影响。结果表明，烧结温度的升高可使磁体得到高致密度，但同时由于其晶粒长大，结果导致磁性能的恶化。在最佳烧结条件下得到磁体的磁性能为Br=1．02T，JHc=220kA／m。磁体具有较好的微观结构，平均晶粒尺寸为20nm。     

Effect of Doping of Ti and C on Crystallization and Magnetic Properties of NdPrFeB Thick Melt-Spun Ribbons

系统研究了添加Ti和C对NdPrFeB合金厚带晶化过程及磁性能的影响。结果表明,Ti的添加可以抑制合金中(Nd,Pr)2Fe23B3亚稳相的生成并细化晶粒从而极大地提高矫顽力;而同时添加Ti和C,随着C含量的增加,矫顽力逐渐降低而剩磁升高。最佳热处理后(Nd0.4Pr0.6)9Fe72Ti4B11C4合金的磁性能达到Jr为0.88T,Hcj为618kA/m,(BH)max为109.8kJ/m3。     

High permeability nano-crystalline FeSiBTaAg ribbons obtained by direct casting

Nano-crystalline soft magnetic ribbons, being extensively used as magnetic cores for switching power supplies, have been invariantly obtained by melt-spinning followed by post-annealing. Reported herewith are the attainment, by direct-casting without annealing, of nano-crystalline Fe_77.4−xSi_15.5B₇Ta_xAg_0.1 (x = 1, 2) ribbons with superior soft magnetic properties (named TAGMET after the addition of Ta and Ag). The grain size of nano-crystalline -FeSi, from 20 to 30 nm, varies with composition and quenching speeds. As-spun Fe_75.4Si_15.5B₇Ta₂Ag_0.1 ribbons consisting of 25 nm nano-crystals exhibit a saturation magnetization of 157 emu/g (1.45 T), an effective permeability of 56,000 at 1 kHz, and coercivity, 8 A/m. With the combination of easier manufacturing process and excellent soft magnetic properties, this alloy is competitive in industrial applications versus the well-known FINEMET.     

Structure and magnetic characterization of amorphous and crystalline Nd–Fe–Al alloys

Glass formation has been studied in Nd₆₀Fe₃₀Al₁₀ alloy produced by melt-spinning, water quenching and copper mold chill casting. Partially amorphous alloys were obtained by melt-spinning at low wheel speeds of 5 to 15 m/s and by water quenching of a 1-mm diameter rod, while fully amorphous alloys were obtained by melt-spinning at higher wheel speeds of 20 and 30 m/s and chill casting of a 1-mm diameter rod. A high coercivity was observed in the partially amorphous ribbon melt-spun at 5 m/s and water quenched rod, and in the fully amorphous chill cast rod, while low values of coercivity were obtained in fully amorphous ribbons melt-spun at high speeds of 20 and 30 m/s. Crystallization of water quenched and chill cast samples after heat treatment at high temperature resulted in a substantial reduction of the high coercivity. Results of X-ray diffraction indicate that formation of Nd and a ternary Fe–Nd–Al phase with an unknown crystal structure were present after crystallization. TEM results and a magnetic study of the heat treated samples indicate that as long as there is an amorphous phase produced by low cooling rate, the high coercivity remains. The high coercivity of bulk amorphous samples is discussed. The unknown ternary Fe–Nd–Al phase is antiferromagnetic with a Neel temperature at about 260 K.     

Magnetron sputtering deposition of [FePt/Ag]n multilayers for perpendicular recording

[FePt/Ag]n multilayers were deposited on glass substrates by RF magnetron sputtering and ex situ annealed at 550℃ for 30 min. The effects of inserted Ag layer thickness and the number of bilayer repetitions （n） on the structure and magnetic properties of the multilayers were investigated. It was found that the difference between in-plane and out-of-plane coercivities varied with an increase of inserted Ag layer thickness in the [FePt 2 nm/Ag x nm]10 multilayers. The ratio of out-of-plane coercivity to in-plane coercivity reached the maximum value with the Ag layer thickness of 5 nm, indicating that the Ag layer thickness plays an important role in obtaining perpendicular orientation. For the [FePt 2 nm/Ag 5 um]n multilayers, perpendicular orientation is also influenced by n. The maximum value of the ratio of out-of-plane coercivity to in-plane coercivity appeared when n was given as 8. It was found that the [FePt 2 nm/Ag 5 nm]8 had a high perpendicular coercivity of 520 kA/m and a low in-plane one of 88 kA/m, which shows a strong perpendicular anisotropy.     

Structural, thermal and magnetic properties of Fe-Si-B-P-Cu melt-spun ribbons: Application of non-isothermal kinetics and the amorphous random anisotropy model

The microstructural variation of Fe-Si-B-P-Cu melt-spun ribbons was analyzed on the basis of non-isothermal kinetics and the amorphous random anisotropy model. The magnitude of latent heat of the crystallization process obtained from DSC curves increases with the increase of quenching wheel speed. The apparent activation energies of the nucleation and growth of α-Fe nanocrystallites increase as the quenching wheel speed increases. Thermal analysis implies that the size of the local short-medium order (cluster) in melt-spun ribbons reduces with the increase of quenching wheel speed. Meanwhile, magnetic measurements display that the coercivity of the stress-released ribbons decreases with the increasing quenching wheel speed. This confirms the thermal analysis results on the basis of the amorphous random anisotropy model. Combing thermal analysis with magnetic measurements, it is believed that the cluster size of the melt-spun ribbons decreases with the increase of the cooling rate during melt-spinning process. Nanocrystalline alloy with desirable microstructure and soft magnetic properties is anticipated to be obtained from an amorphous alloy prepared at an appropriate cooling rate by adjusting the quenching wheel speed.