纳米晶复合Nd10Fe76B10Nb4-xZrx（x=0～4）永磁合金的磁性能研究

采用熔体快淬法制备了成分为Nd10Fe76B10Nb4-xZrx(x=0～4)的合金条带,退火处理后得到了纳米晶复合永磁合金。利用振动样品磁强计(VSM)分析了该合金体系的退磁曲线、磁交互作用曲线(δM-H曲线)、磁化率χ随外加磁场变化曲线,研究了其磁性能及软、硬磁性相间的交换耦合作用的变化。结果表明,添加适量的Zr元素可细化晶粒,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Zr含量为2%(原子分数)时,制得的合金具有最佳的综合磁性能:jHc=1059.16kA/m,Br=1.08T,(BH)max=185.72kJ/m3。     

NdFeB纳米晶双相复合永磁合金

概述了NdFeB纳米晶双相复合永磁合金的发展状况,对前当的研究动向做了介绍和分析。     

纳米晶复合Nd9.5Fe76Co5Zr3-xNbxB6.5（x=0～3.0）粘结磁体的磁性能和温度系数的研究

采用熔体快淬法及真空退火工艺制备了Nd9.5Fe76Co5Zr3-xNbxB6.5(x=0～3.0)粘结磁体,研究了其磁性能及温度系数。结果表明,随着Nb含量的增加,合金剩磁逐渐提高,磁能积和矫顽力呈现先增大后减小的趋势。Zr元素与Nb元素复合添加,能够有效地改善矫顽力温度系数β。经最佳条件退火处理后制备的Nd9.5Fe76Co5Zr1.5Nb1.5B6.5的粘结磁体,具有最优的综合磁性能:Br=0.717T,Hcj=773kA/m,(BH)max=82kJ/m3,α20～150℃=-0.111%/℃,β20～150℃=-0.356%/℃。     

纳米晶复合Nd8.5Fe76.6-xGaxCo5Zr2.7B6.2(x=0～0.5) 粘结磁体磁性能的研究

采用快淬和晶化退火法制备了成分为Nd8.5Fe76.6-xGaxCo5Zr2.7B6.2(x=0～0.5)的纳米晶复合永磁粘结磁体,研究了其磁性能的变化.结果表明,适量Ga元素的添加能有效提高磁体退磁曲线的方形度,进而提高磁体的最大磁能积.Ga含量0.2%(原子分数),快淬速度为16.0m/s的合金经670℃/4min的晶化处理后,制得的粘结磁体具有较佳的磁性能:Br=0.745T,jHc=730.1kA/m,(BH)max=80.1kJ/m3.适量的Ga元素的添加可以提高磁体的温度稳定性.Ga含量为0.2%(原子分数)的合金具有较好的温度系数,在25～150℃温度区间内剩磁温度系数α=-0.091%/℃,内禀矫顽力温度系数β=-0.353%/℃.     

α-Fe/Nd2Fe14B复合纳米晶合金的X射线定量相分析

采用联立方程组确立了α-Fe/Nd2Fe14B复合纳米晶合金中相含量的计算方法.该方法运用最小二乘回归法和抛弃平均法消除病态方程组.将其应用于α-Fe/Nd2Fe14B复合纳米晶合金的相含量计算,所得结果与直接对比法一致.     

纳米晶双相Nd3.6Pr5.4Fe83-xGaxCo3B5合金磁性能的研究

用熔体快淬法制备Nd3.6Pr5.4Fe83-xGaxCo3B5(%(原子分数),x=0～1.0)纳米晶双相永磁材料,研究其磁性能的变化.结果表明适量的添加Ga(x=0.25)可以细化晶粒,使快淬薄带中的Nd2Fe14B硬磁相和α-Fe软磁相发生较充分的交换耦合作用,获得较优异的磁性能,Ga含量过多或过少的快淬薄带的磁滞回线出现缩颈现象,低温退火使得该现象得以改善.     

Nd2Fe14B/(α-Fe,Fe3B)复合纳米晶的生长动力学研究

采用X射线衍射分析(XRD)研究了Fe-Co-Nd-Dy-B非晶合金晶化过程中α-Fe、Fe3B纳米晶的生长动力学.根据纳米晶生长达到稳定状态所需的时间常数tE与退火温度Ta的关系,计算了α-Fe和Fe3B纳米晶的生长激活能为Egα-Fe=95±2 kJ/mol和E Fe3B=133±13 kJ/mol.该值远小于α-Fe和Fe3B两相的表观晶化激活能Ecα-Fe=555 kJ/mol和EcFe3B=481 kJ/mol.这表明Fe-Co-Nd-Dy-B非晶合金晶化过程中α-Fe和Fe3B纳米晶的形成主要由成核所控制.     

低频脉冲磁场对非晶合金Fe78Si9B13稳定性的影响

对非晶合金Fe78Si9B13进行了低频脉冲磁场处理,用Mossbauer谱仪、透射电镜等方法,观察处理试样的微观结构变化,用DTA方法研究了低频脉冲磁场对非晶合金Fe78Si9B13稳定性的影响;结果表明低频脉冲磁场可促进非晶合金发生纳米晶化,且处理后的试样与制备态相比其表观激活能有所提高,从而改善了原始非晶合金的稳定性.     

α-Fe/Nd2Fe14B复合纳米晶的织构形成研究

采用X射线衍射分析(XRD)技术,研究了NdprFeCoB熔体快淬所制备的α-Fee/Nd2Fe14B纳米晶的织构形成过程.结果表明,Nd2Fe14B纳米晶具有较强的(001)织构,而α-Fe纳米晶具有(110)织构,这些织构垂直于薄带表面,且从自由面到激冷面逐渐减弱.从自由面到激冷面,Nd2Fe14B相在(001)晶面法线方向的尺寸和α-Fe相在(220)晶面法线方向的尺寸逐渐减小.在激冷面各晶面法线方向的尺寸相近,表明纳米晶的形状近似于等轴晶.α-Fe/Nd2Fei4B纳米晶织构的形成和生长受合金薄带在凝固过程中热流梯度的控制.     

Cr替代Co对Fe3B/Nd2Fe14B纳米复合磁体微观结构与磁性能的影响

主要研究了添加Cr置换Nd5Fe72.3Cu0.2Co4B18.5合金中的Co元素对Fe3B/Nd2Fe14B型纳米复合永磁体磁性能与微观结构的影响.结果表明相应于Co元素而言,添加Cr元素可有效细化NdFeB合金软、硬磁性相的晶粒尺寸;随退火温度的升高,添加Cr元素的Nd5Fe72.3Cu0.2Cr4B18.5合金的jHc值随退火温度的变化不明显.DTA曲线分析表明,NdFeCuCoB具有一个放热峰,而NdFeCuCrB具有两个放热峰.NdFeCuCrB非晶合金在650℃退火处理30min可获得最佳磁性能Br=0.944T,jHc=383kA/m,(BH)max=77.5kJ/m3.     

Ni55.30Fe17.60Ga27.10磁致形状记忆合金马氏体相变

研究了热处理对Ni55.30Fe17.60Ga27.10磁致形状记忆合金组织和马氏体相变的影响.电弧态合金组织中马氏体板条模糊.在氩气保护,800℃保温4h缓慢冷却条件下热处理后,马氏体板条规整平直.DSC结果表明Ni55.30Fe17.60Ga27.10合金在加热/冷却时发生热弹性马氏体相变.热处理后Ms=43.24℃,Mf=36.72℃,As=46.84℃,Af=51.83℃.相比电弧态,热处理后合金Ms和Mf提高,As和Af降低,相变滞后减小.XRD结果证明热致马氏体为14M马氏体.     

(Fe50Co50)73.5Cu1Nb3Si13.5B9合金的微观结构及软磁性能

研究了(Fe50Co50)73.5Cu1Nb3Si13.5B9合金晶化过程中的微观结构及形成纳米晶后的合金软磁性能,发现在FINEMET合金基础上,用Co置换1/2含量Fe形成的(Fe50Co50)73.5Cu1Nb3Si13.5B9非晶合金具有相对较高居里温度Tc≈450℃,460℃退火处理后(Fe50Co50)73.5Cu1Nb3Si13.5B9合金形成均匀纳米晶组织,晶粒度约为20nm.     

Effect of addition of aluminum on the evolution of microstructure in HITPERM class Fe44Co44Zr7B4Cu1 alloy

The paper reports the effect of the addition of small amount of Al on the microstructure and properties of HITPERM class rapidly solidified Fe₄₄Co₄₄Zr₇B₄Cu₁ glassy alloy. Using three dimensional atom probe measurements we present evidence for the formation of Cu clusters on annealing in the metallic glass matrix of the Al containing alloy Fe₄₃Co₄₃Al₂Zr₇B₄Cu₁. Such clusters are otherwise absent in the parent alloy under similar conditions. The Cu clusters provides heterogeneous nucleation sites for the formation of bcc α′-FeCo phase leading to an increase in number density of this nanocrystalline phase and thereby enhancing the magnetic properties.     

Cooling rate induced variation in microstructure and magnetic structure of Nd60Fe30Al10 glass forming alloy

Cooling rate induced variation in microstructure and magnetic structure was investigated in the as-cast Nd₆₀Fe₃₀Al₁₀ alloy. Because the cooling rate was different from the periphery to the center regions, apparent evolution from a full amorphous to a partial precipitated crystalline structure was observed in one as-cast sample. Corresponding to different microstructures, two magnetic domain structures, i.e. fine strip-like domains in sub-micron scale and sunflower-like domains in micron scale, were observed at the periphery and the center of a cross section, respectively. The variation of magnetic properties was discussed in the view of exchange interaction coupling.     

Ag、Cu添加对Fe40Co40Zr6Mo4B10合金热稳定性和磁性能的影响

采用单辊快淬法制备Fe40Co40Zr6Mo4B10、Fe40Co40Zr6Mo4B9Ag1和Fe40Co40Zr6Mo4B9Cu1三种非晶合金,在不同温度下对3种合金进行热处理。利用DSC、XRD、VSM对合金的热性能、微观结构和磁性能进行测试。结果发现,Ag和Cu元素的添加均提高了合金的热稳定性,同时也降低了合金的矫顽力。Cu元素的添加作用更为明显。Fe40Co40Zr6Mo4B9Cu1合金具有相对高的热稳定性能和低的矫顽力。     

Magnetic properties of Fe78.4Si9.5B9Cu0.6Nb2.5 nanocrystalline alloy powder cores

The microstructure and morphology of nanocrystalline Fe_78.4Si_9.5B₉Cu_0.6Nb_2.5 alloy powders prepared by ball milling technique were characterized by X-ray diffraction and scanning electron microscopy studies. The effective permeability (μ_e), quality factor (Q), DC bias property, and core losses of the corresponding powder cores were tested using low capacitance resonator meter and B–H analyzer in the range of 1–1000 kHz. The results show that the relative density and compression strength of the powder cores increased with increasing particle size. Powder cores from large size particles (150–300 μm) were found to exhibit higher μ_e and core loss, but lower Q level when compared to samples of small size ones (5–40 μm). Moreover, the μ_e of powder cores with large particles reached a peak value with the addition of 2 wt% glass binder. The Q value was also found to be proportional to the binder content except 10 wt%, while its peak position was shifted toward higher frequency.