Fe64-xCoxNd7B25Nb4（x=0～40）块体合金的晶化过程和磁性能研究

采用铜模吸铸法制备了Fe64-xCoxNd7B25Nb4(x=0～40)块体合金,利用X射线衍射仪(XRD)、差示扫描量热仪(DSC)和振动样品磁强计(VSM)研究了该体系合金的非晶形成能力、晶化过程和磁性能。结果表明:Fe64-xCoxNd7B25Nb4(x=0～40)块体合金具有良好的非晶形成能力。在Co含量为0at%～40at%范围内,合金基本为非晶态。该系合金铸态时为软磁性,晶化处理后则表现为硬磁性。随着Co含量的不同,合金的晶化行为和晶化后的产物及对应的磁性能均有明显的变化。不含Co元素时,合金发生两级晶化反应;晶化过程中出现了亚稳相Fe23B6,随着退火温度的升高,Fe23B6分解为Fe3B和α-Fe相。添加Co元素后,合金只发生一级晶化反应。Co含量为20at%的合金在1 003 K退火后,内禀矫顽力高达1 164 kA/m。     

Nb对Fe-Co基合金非晶形成能力及磁性能的影响

利用铜模吸铸法制备(Fe0.5Co0.5)71-xNbxZr3Nd4B22(x=0~10)系块体合金,研究合金元素Nb的添加对该体系合金非晶形成能力(GFA)和磁性能的影响。结果表明,适当Nb的添加能有效提高合金的非晶形成能力。当Nb含量为5at%时,可获得具有完全非晶结构的块体非晶合金,该合金呈现典型的软磁性能,饱和磁化强度(Ms)为79 Am2/kg;合金的晶化温度(Tx)为957 K,晶化激活能E为538.30 kJ/mol。     

Nb对Zr基块体非晶合金热稳定性、非晶形成能力及机械性能的影响

利用水冷铜模铸造法成功制备了(Zr70Ni10Cu20)90-xNbxAl10(x=0,2,5,7)块体非晶合金,采用XRD,DSC和DTA研究了Nb对该合金体系热稳定性和非晶合金形成能力(GFA)的影响．结果表明,适量Nb的添加可有效提高该合金的GFA和热稳定性．当Nb含量为x=2时,合金具有最宽的过冷液态区(△Tx=119K)和最大的非晶形成能力(参数γ=Tx／(Tg T1)=0．435),Nb的适量添加也有利于提高块体非晶合金的强度和塑性应变,其中x=2的块体非晶的抗压强度和断裂应变量分别达到1783MPa和11．1％。     

FeNbYB非晶合金的晶化过程及磁性能

用单辊快淬法制备Fe74Nb6-xYxB20(x=3 at%、4 at%、5 at%)非晶合金,取不同的温度对合金热处理,利用差热分析仪(DTA)、X射线衍射仪(XRD)、透射电子显微镜(TEM)、振动样品磁强计(VSM)研究了合金的非晶形成能力、晶化过程和磁性能。结果表明,添加微量Y元素提高了合金的非晶形成能力,当Y含量为5 at%时,Fe74Nb1Y5B20非晶合金过冷液相区具有最大值、△Tx=63℃。Fe74Nb6-xYxB20(3 at%、4 at%、5 at%)合金的晶化过程为:非晶→非晶+α-Fe+Fe23B6+Fe2B→α-Fe+Fe23B6+Fe2B。随着退火温度的升高,3种合金Fe74Nb6-xYxB20(x=3 at%、4 at%、5 at%)饱和磁化强度MS变化趋势是一致的,在670℃退火后3种合金MS均达到最大、分别为128、122、134 A·m2·kg-1,矫顽力Hc为2.96、3.12、3.36 kA·m-1,在750℃退火后,Hc快速增大。     

铜模吸铸法制备Fe-Nd-Al-B-Dy合金的结构和磁性能

为了进一步改善Fe-Nd-Al-B非晶合金的非晶形成能力和磁性能,研究添加Dy元素对此体系合金的显微结构、磁性能以及晶化行为的影响.利用铜模吸铸法制备厚度为1mm的片状(Fe0.51Nd0.35Al0.10b0.40)100-xDyX(x=0,1,3,6)合金.采用示差扫描量热法(DSC),振动样品磁强计(VSM)和X射线衍射仪(XRD)研究Dy对该系列合金非晶形成能力、磁性能和晶化行为的影响.结果表明,添加少量Dy元素使得合金Fe-Nd-Al-B-Dy的磁性能各项指标大幅度提高,得到较好的硬磁性.然而,当进一步提高Dy含量到6%时,合金呈现顺磁性.Fe-Nd-Al-B-Dy系合金晶化后,磁性能会发生很大转变,其中具有较好硬磁性的(Fe0.51Nd0.35Al0.10B0.04)99Dy1合金在完全晶化后呈现为顺磁性.     

Nb对Cu-Zr-Al-Y块体非晶组织结构和力学性能的影响

利用铜模喷铸工艺制备了准2mm棒状(Cu45Zr45Al6Y4)100-xNbx(x=0,1 at%,2 at%,3 at%)合金试样。通过对试样进行XRD、DSC、单轴压缩、SEM及EDS分析,探究了Nb的添加对Cu45Zr45Al6Y4-合金非晶形成能力、组织结构以及力学性能的影响。结果表明:Nb降低该合金系的非晶形成能力(GFA),促进晶相析出;1at%Nb添加有利于在(Cu45Zr45Al6Y4)100-xNbx块体非晶基体内获取高体积分数的B2-Cu Zr强韧相,从而明显提高了合金的室温塑性。     

[Fe_(0.71)(Dy_xNd_(1-x))_(0.05)B_(0.24)]_(96)Nb_4(x=0-1)块体合金的非晶形成能力和磁性能

采用铜模吸铸法制备[Fe0.71(DyxNd1-x)0.05B0.24]96Nb4(x=0-1,摩尔分数)块体合金,利用X射线衍射(XRD)、差示扫描量热仪(DSC)和振动样品磁强计(VSM)研究合金的非晶形成能力(GFA)和磁性能。结果表明:该体系合金均具有较好的非晶形成能力,可制备出直径为2 mm的完全非晶合金,随着Dy含量(x)的增加,合金的非晶形成能力逐渐增强。当x=1时,可制得直径为3 mm的完全非晶合金;饱和磁化强度(Ms)由x=0时的Ms=97.59 A·m2/kg逐渐降低到x=1时的Ms=75.85 A·m2/kg。该体系直径为2 mm的块体非晶合金均表现为明显的软磁性特征。     

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。     

铜模吸铸法制备Fe-Nd-Al-B-Nb合金的结构和磁性能的研究

利用铜模吸铸法制备了厚度为1 mm片状的[(Fe0.53Nd0.37Al0.1)96B4]100-xNbx(x=0,2,4,6,8)合金.采用示差扫描量热法(DSC),振动样品磁强计(VSM)和X射线衍射(XRD)仪研究了Nb对该合金非晶形成能力、热稳定性和磁性能的影响.结果表明,Nb元素的添加可以有效提高合金的非晶形成能力和热稳定性,且显著提高了合金的饱和磁化强度.一定量的Nb元素(≥4at%)将抑制合金中Nd2Fe14B硬磁相的析出,使合金的磁性能从硬磁性转变成软磁性.     

纳米晶复合Nd_(9.5)Fe_(79-x)Co_5Nb_xB_(6.5)(x=0,1,2,3)永磁合金的微结构和磁性能

利用X射线衍射仪(XRD)、振动样品磁强计(VSM)、透射电子显微镜(TEM)和三维原子探针(3DAP)等研究了Nb元素对纳米晶复合Nd_(9.5)Fe_(79-x)Co_5Nb_xB_(6.5)(x=0,1,2,3)永磁合金微结构和磁性能的影响。结果表明,随着Nb元素的增加,合金的剩磁J _r首先增加,在Nb含量为1 at%时达到最大值0.94 T,继续增加Nb元素后,合金的剩磁开始下降;矫顽力_i H_c则随着Nb元素的增加逐步增加,当Nb含量超过2 at%后,增加幅度变缓;合金的最大磁能积(BH)_(max)随着Nb元素的增加先增加后降低,纳米晶复合Nd_(9.5)Fe_(79-x)Co_5Nb_xB_(6.5)合金具有最优的综合磁性能,即J_r=0.91 T,_i H_c=663k A/m,(BH)_(max)=120 k J/m~3。Nb元素在合金的晶化过程中富集于晶间形成Nb Fe B相,有利于细化晶粒尺寸,从而提高合金的磁性能。     

Effect of Nd substitution on the soft magnetic properties of a nanocrystalline Fe84Nb7B9 Alloy

The substitution effect of Nd for Nb on the structure and magnetic properties of a Fe₈₄Nb₇B₉ alloy has been investigated. The substitution of Nd causes the formation of Fe₃B phase in the as-quenched state; Decrease the crystallization temperature and increase the Curie temperature of the amorphous phase. After annealing at an optimum temperature; The soft magnetic properties are improved by substitution of 0.05 to 0.4 at% Nd and Fe₈₄Nb_6.9Nd_0.1B₉ alloy exhibits the permeability (μ′) at 1kHz of 39000 and the coercivity (H_c) of 4.3 A/m.     

Glass forming ability and microstructure of hard magnetic Nd60Al20Fe20 glass forming alloy

Glass forming ability (GFA), magnetic properties and microstructure of Nd₆₀Al₂₀Fe₂₀ as-cast rod were investigated and further compared with Nd₆₀Al₁₀Fe₃₀ glass forming alloy. The rod prepared by suction casting with a diameter of 3 mm exhibits the typical amorphous nature in XRD pattern, distinct glass transition in DSC traces and hard magnetic properties. It is found that the diameter of cast Nd₆₀Al₂₀Fe₂₀ glassy rod is much larger than the critical section thickness (Z_c) of bulk metallic glass (BMG) predicted from DSC measurements. A few nano-crystalline particles with the structure and composition similar to A_x phase in Nd–Fe alloys were found embedded randomly in amorphous matrix and could be the origin of hard magnetic properties of the as-cast rods. The GFA of the alloy appears to be enhanced by the precipitation of metastable nano-particles with small positive forming enthalpy and the real Z_c of the alloy could be less than 1 mm predicted by parameter γ.     

Microstructural characteristics of Nd2Fe14B/α-Fe nanocomposite ribbons bearing Nb element

The effects of Nb on the microstructure and magnetic properties of (Nd_0.9Dy_0.1)_9.5Fe_79-xCo₅Nb_xB_6.5 (x = 0, 1) nanocomposite magnets were investigated. A fine and uniform microstructure was achieved for the ribbons annealed at 710°C for 4 min, enhancing the interaction coupling between grains and improving the magnetic properties. The results of three-dimensional atom probe (3DAP) indicated that Fe-Nb-B intergranular phase existed at the grain boundaries, suppressing the grain growth during the crystallization process. The coercivity was improved from 224 to 643 kA/m for the modification of the microstructure.     

Microstructure of hard magnetic bccFe/NdFeB nanocomposite alloys

The microstructure of amorphous-phase remaining bccFe/NdFeB nanocomposite Nd_vFe_balCo₈Nb_xCu_yB_z (V = 6–8, x = 0–2.5, y = 0–0.5 and z = 6–7 at%) magnet alloys, which were prepared by melt spinning, was investigated by means of high resolution transmission electron microscopy (HR-TEM), three-dimensional atom probing (3DAP), and Mössbauer spectroscopy. It was found by HR-TEM that a small amount of amorphous phase remains in the intergranular region between crystal grains of bccFe and Nd₂Fe₁₄B₁ even after heat treatment at 740°C. The results of 3DP showed that Nb and B atoms are significantly enriched in the remaining amorphous phase. Mössbauer spectroscoopy revealed that the intergranular region is composed of not only so called amorphous phase but also several thin layered phases which have a rather strong hyperfine field distinctivity, and that the relative existing ratios of both the total intergranular phases and the Nd₂Fe₁₄B₁ phase increase with increasing Nb content. The coercivity-enhancing effect of Nb addition is discussed in this paper.     

Effects of Nb and C additions on the crystallization behavior, microstructure and magnetic properties of B-rich nanocrystalline Nd–Fe–B ribbons

The effects of Nb and C additions on the crystallization behavior, microstructure and magnetic properties of B-rich Nd_9.4Fe_79.6−xNb_xB_11−yC_y (x = 0, 2, and 4; y = 0, 0.5, and 1.5) alloy ribbons have been investigated. The results show that Nb and C additions change the crystallization behavior of Nd_9.4Fe_79.6B₁₁, avoid the formation of metastable Nd₂Fe₂₃B₃ phase, leading to the simultaneously precipitation of α-Fe and Nd₂Fe₁₄B phases. The results also show that Nb and C additions suppress the formation and growth of the soft α-Fe phases, leading to the presence of a large amount of Nd₂Fe₁₄B phases. Nb and C additions also refine the structure, and thus increase the exchange coupling interaction between the soft and hard phases. Excellent magnetic properties of B_r = 0.85 T, _iH_c = 1106 kA/m, and (BH)_max = 117 kJ/m³ have been achieved in Nd_9.4Fe_75.6Nb₄B_10.5C_0.5 alloy ribbons.     

Glass-forming ability and thermal stability of Nd70−xFe20Al10Yx alloys

The glass-forming ability (GFA) and thermal stability of Nd_70−xFe₂₀Al₁₀Y_x (0≤x≤15) alloys produced by melt spinning and copper-mold casting have been investigated. Ribbon samples in the composition range show a fully amorphous structure. Except Y=5 at.%, bulk amorphous alloys at least 2 mm in diameter were obtained. Both the amorphous ribbon and the bulk cylinder for the Nd₅₅Fe₂₀Al₁₀Y₁₅ alloy show a distinct glass transition temperature and a wide supercooled liquid region before crystallization. It is suggested to use a new parameter to characterize both the GFA and the thermal stability of Nd–Fe–Al–Y alloys, showing that Nd₆₀Fe₂₀Al₁₀Y₁₀ alloy is the best one both in GFA and thermal stability. The remanence (J_r), magnetization (J₁₅₀₀), and coercivity (H_c) for the as-cast Nd_70−xFe₂₀Al₁₀Y_x amorphous cylinders depend strongly on the composition. The enhanced GFA and thermal stability as well as the reduction of magnetic properties are discussed.     

Quaternary Fe-based bulk metallic glasses with a diameter of 5 mm

Bulk metallic glasses with a diameter of 5 mm were obtained by drop casting in the quaternary Fe–B–Y–Nb and Fe–B–Y–Mo systems. Starting from the best glass former Fe_71.2B₂₄Y_4.8 in the ternary Fe–B–Y system, the search quickly led to the discovery of the quaternary good glass formers (Fe_71.2B₂₄Y_4.8)₉₆Nb₄, (Fe_73.2B₂₂Y_4.8)₉₅Mo₅ and (Fe_70.7B₂₄Y_5.3)₉₅Mo₅ after trying only around a dozen of alloys. No obvious glass transition event was observed for these quaternary alloys. No Nb and Mo containing crystalline phases were detected in the alloys studied. The potential beneficial effects of Nb and Mo in enhancing the glass forming ability (GFA) of the Fe–B–Y alloy system are discussed.     

The magnetic, structure and mechanical properties of rapidly solidified (Nd7Y2.5)-(Fe64.5Nb3)-B23 nanocomposite permanent magnet

The Nd₇Y_2.5Fe_64.5Nb₃B₂₃ nanocomposite permanent magnets in the form of rods with 2 mm in diameter have been developed by annealing the amorphous precursors produced by copper mold casting technique. The phase evolution, structure, magnetic and mechanical properties were investigated with X-ray diffractometry, differential scanning calorimetry, electron microscopy, magnetometry and universal uniaxial compression strength techniques. The heat treatment conditions under which the magnets attained maximum magnetic and mechanical properties have been established. The results indicate that magnet properties are sensitive to grain size and volume content of the magnetic phases present in the microstructure. The composite microstructure was mainly composed of soft α-Fe (20-30 nm) and hard Nd₂Fe₁₄B (45-65 nm) magnetic phase grains. The maximum coercivity of 959.18 kA/m was achieved with the magnets annealed at 760 °C whereas the highest remanence of 0.57 T was obtained with the magnets treated at 710 °C. The optimally annealed magnets possessed promising magnetic properties such as _jH_c of 891.52 kA/m, B_r of 0.57 T, M_r/M_s = 0.68, (BH)_max of 56.8 kJ/m³ as well as the micro-Vickers hardness (H_v) of 1138 ± 20 and compressive stress (σ_f) of 239 ± 10 MPa.     

Microstructure and properties of nanocrystalline Fe–Zr–Nb–B soft magnetic alloys with low magnetostriction

We have investigated the microstructure–property relationship of nanocrystalline Fe₈₅Zr_1.2Nb_5.8B₈ and Fe_85.5Zr₂Nb₄B_8.5 soft magnetic alloys in order to understand the origin of drastic change in the permeability regardless of the zero magnetostriction in these two alloy compositions. Plan-view and cross-section transmission electron microscopy (TEM) observations showed strongly textured α-Fe particles on the free surface of the Fe₈₅Zr_1.2Nb_5.8B₈ alloy ribbon, while uniform nanocrystalline microstructure was observed in the Fe_85.5Zr₂Nb₄B_8.5 alloy ribbon. The high Zr content of the latter improves the glass forming ability, thereby suppressing the surface crystallization, resulting in higher permeability. By adding Cu in the Fe–Zr–Nb–B alloy, uniform nanocrystalline microstructure was obtained, from which superior soft magnetic properties with zero magnetostriction was achieved.     

Magnetic Properties of the Nanocrystalline Nd-Ho-Fe-Co-B Alloy at Low Temperatures: The Influence of Time and Annealing

A study is made of the effects of various factors such as time (7 years), temperature, high magnetic field up to 580 kOe and heat treatment (HT) on the morphological structure and magnetic hysteresis properties of a high-coercive nanocrystalline (Nd_0.55Ho_0.45)_2.7(Fe_0.8Co_0.2)₁₄B_1.2 alloy with a low temperature coefficient of remanence. We find a rather weak time effect on (Nd_0.55Ho_0.45)_2.7(Fe_0.8Co_0.2)₁₄B_1.2. After 7 years, the loss in the maximum magnetic energy product (BH)_max is no more than 5%. Annealing of the sample at 250 °C for 30 min decreases the amount of amorphous phase from 7.2 to 1.7%, while the grains’ size of the 2-14-1 phase increases from 83 to 109 nm. For the HT alloy, a magnetization jump is observed at H ~500 kOe. It can be attributed to the first-order magnetization process or a spin-flip magnetic transition. Rectangularity of the hysteresis loop degrades after annealing. In case of the short-time heat treatment, losses in (BH)_max are ~10%.