Fe25Co25Pt25B25高熵纳米复相永磁体的组织结构与磁性能

采用液态急冷法制备了高熵Fe₂₅Co₂₅Pt₂₅B₂₅合金,研究了其热处理前后的组织结构及磁性能。结果表明：Fe₂₅Co₂₅Pt₂₅B₂₅高熵合金具有较高的非晶形成能力,液态急冷合金形成了非晶态结构,表现出软磁特性。Fe₂₅Co₂₅Pt₂₅B₂₅高熵非晶合金热处理结晶化过程为：非晶相→非晶相+fcc-(Fe, Co)Pt相→非晶相+fcc-(Fe, Co)Pt+L1₀-(Fe, Co)Pt+(Fe, Co)₂B相→非晶相+L1₀-(Fe, Co)Pt+(Fe, Co)₂B相→L1₀-(Fe, Co)Pt+(Fe, Co)₂B相。经843 K热处理900 s后,Fe₂₅Co     

Fe72-xNd7B21Nbx(x=0~4.0)块体合金晶化过程和磁性能的研究

采用铜模吸铸法制备了直径为2mm的Fe_(72-x)Nd_7B_(21)Nb_x(x=0~4.0)块体合金,利用X射线衍射仪(XRD)、差示扫描量热仪(DSC)、振动样品磁强计(VSM)和多功能物理性质测量系统(PPMS)研究了Nb含量对该体系合金非晶形成能力、晶化行为及磁性能的影响。结果表明:适当的添加Nb有助于提高该体系合金的非晶形成能力,当Nb含量为2.0at%,2.2at%和2.5at%时,可以获得基本为非晶结构的块体合金。Nb含量对该体系合金的晶化行为有着重要影响,Nb含量为2.5at%的合金在晶化过程中能有效抑制非磁性相的析出,增强了晶粒间的交换耦合作用,使得其剩磁得到明显的提高,具有最佳的综合磁性能:B_r=0.63T,H_(ci)=448.97kA/m,(BH)_(max)=36.32kJ/m~3。     

纵向磁场退火处理对Fe73.7Si15.3Cu1Nb3B7合金组织结构和性能的影响

研究了纵向磁场不同温度退火处理对组成为Fe_73.7Si_15.3Cu₁Nb₃B₇的1k107B纳米晶合金带材的组织结构和软磁性能的影响。结果表明：在纵向加磁电流为150 A、退火温度区间为525～595℃时,合金的矩形比均在0.97以上,晶粒尺寸(D)和矫顽力(H_c)小幅度增加,最大磁导率(μ_m)则与之相反,损耗(P_s)在575℃时取得最小值(99 W/kg@50 kHz, 0.4 T);有效磁导率(μ_e)随着退火温度的升高呈先增加后减小的趋势;通过磁光克尔显微镜观察到纵向磁场退火后合金内部形成规则的平行于磁场方向的条纹畴,且随着退火温度的升高磁畴壁厚度逐渐增大。     

退火温度对FeCuNbSiB纳米晶合金磁性能的影响

用熔体快淬法制备出3种FeCuNbSiB纳米晶合金带材,绕制成50 mm×32 mm×20 mm的环形磁环,随后在530~620℃下进行等温退火,研究退火温度对合金磁性能的影响。结果表明:随着退火温度的增加,合金内部晶化相的晶粒尺寸和体积分数有所增加。在550~600℃等温退火后合金具有相对较低的矫顽力(Hc为1.0~1.5 A/m,测试条件:Bm=100 mT,f=10 kHz)和损耗值(Pm为1.4~1.8 W/kg,测试条件:Bm=300 mT,f=10 kHz),特别是经过570~590℃退火后合金在1 kHz^50 kHz频率范围内具有最佳的磁导率。同时,在1 kHz^10 MHz频率范围内,不同测试频率下合金阻抗值对应的最佳退火温度也不同。     

Fe83Ga17Dyx合金组织结构及磁致伸缩性能

研究了Fe83Ga17Dyx(x=0,0.2,0.4,0.6)系列合金的晶体结构、显微组织、磁致伸缩性能。结果表明,稀土Dy添加到Fe83Ga17合金中对合金的晶体结构影响很小,对显微组织影响显著。Fe83Ga17合金中添加稀土Dy后,性能最好的Fe83Ga17Dy0.2合金在5000 Oe外加磁场下,磁致伸缩系数达到300×10-6。     

合金成分对Pr2Fel4B／α—Fe纳米复合永磁材料组织与磁性的影响

用XRD、TEM、Mossbauer谱和VSM等实验方法，研究了不同Pr含量、B含量和Cu含量的Pr2Fe14B／α—Fe型纳米复合快淬带的显微结构与磁性。结果表明：PrxFe94-x，B6合金在x＝8(α—Fe体积分数约30％)时磁性能最佳，Br＝1．29T，Hci＝461．7kA／m，(BH)man＝165．6kJ／m^3；Pr6．5(Fe8．5Co0．2)86．5—xCuxB5合金在x＝0．5时获得最佳的磁性能；随B含量增加，富B相在晶界分布，Pr8Fe92-xBx交换耦合减弱，磁性能单调下降。     

微量B元素添加对Fe81Ga19合金磁致伸缩性能的影响

本文采用真空熔炼法制备(Fe₈₁Ga₁₉)_1-xB_x(x=0,0.06,0.1,0.15,0.20)系列铸态合金,通过X射线衍射、扫描电镜及配套的能量色散谱、金相显微镜表征合金的微观结构、形貌及成分,利用电阻应变片法测量合金的磁致伸缩性能。结果表明,微量的B元素添加提高了合金的磁致伸缩性能, 在x=0.10时最大达到最大饱和磁致伸缩值λs=138ppm。研究表明,(Fe₈₁Ga₁₉)_1-xB_x合金结构为α-Fe体心立方为主。B元素的添加,一部分进入晶格间隙,引起晶格畸变,提高合金磁致伸缩性能,另一部分以富B析出相的形式分布在晶粒内部;合金添加B元素后,晶粒变为对磁致伸缩性能有利的大柱状晶,大柱状晶由于晶界少,减少阻碍磁畴运动的因素,有利于合金的磁致伸缩性能。     

合金元素对PrFeB永磁合金结构和磁性能的影响

简述了Co、Nb、Zr、Ga、Cu、Si等合金元素的加入对PrFeB永磁合金的结构和磁性能的影响。以上合金元素的加入，均能不同程度地提高PrFeB的磁性能，但含量超过一定比例后，永磁合金磁性能则有所下降。Co、Cu、Si的加入还有助于PrFeB合金居里温度的提高。     

Fe90-xNb8Zr2Bx(x=10,20)合金的热行为、结构及磁性能

采用单辊快淬法制备两种不同B含量的Fe_90-xNb₈Zr₂B_x(x=10, 20)非晶合金,在各自晶化峰值温度进行1 h的等温热处理得到相应的纳米晶合金。利用同步热分析仪(STA)、透射电镜(TEM)、X射线衍射仪(XRD)和振动样品磁强计(VSM)等研究了两种合金的热行为、结构及磁性能,并进行对比分析。结果表明：两种合金快淬态时均处于完全非晶态,两种非晶合金的差示扫描量热(DSC)曲线存在较大差别,低B含量的合金中没有观察到过冷液相区,而在高B含量的合金中观察到过冷液相区。两种合金具有明显不同的晶化过程,低B含量合金的晶化过程分为3个阶段,高B含量合金的晶化过程分为两个阶段。Fe₈₀Nb₈Zr₂B₁₀合金在晶化的第二个阶段获得相对较好的软磁性能。Fe₇₀Nb₈Zr₂B₂₀合金在晶化的第一个阶段获得相对较好的软磁性能。     

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。     

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.     

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.     

Milling and subsequent thermal annealing effects on the microstructural and magnetic properties of nanostructured Fe90Co10 and Fe65Co35 powders

The influence of milling and subsequent annealing on the microstructural and magnetic properties of Fe₉₀Co₁₀ and Fe₆₅Co₃₅ alloys is investigated. After milling for 8 h a body-centred cubic nanostructured Fe–Co alloy forms with an average crystallite size of about 12 nm. The magnetization saturation (M_S) increases 16% for Fe₆₅Co₃₅ and 5% for Fe₉₀Co₁₀ alloys by milling for 8 h. Subsequent annealing of Fe₉₀Co₁₀ and Fe₆₅Co₃₅ powders for 105 min at 550 °C improves the M_S about 6 and 11%, respectively. Before annealing, the coercivity increases (up to 60 Oe) by milling for 3 h, followed by a reduction on milling for longer periods (45 h). At the initial stage of the heating, a sharp decrease in H_C to 8–10 Oe occurs due to the relief of internal strain. Further heating leads to an increase in the coercivity (intermediate times) followed by a slight diminution on heating for final stage.     

Ce17Fe78-xB6Mx (M=Cu, Al, Ga; x=0-1.0)快淬合金永磁性能研究

本文基于熔体快淬技术,研究了低熔点元素Cu、Al和Ga添加对Ce₁₇Fe₇₈B₆合金磁性能的影响。三类低熔点元素的加入,均降低了合金的磁化强度,而矫顽力有一定程度的提升。其中,Cu和Ga元素添加可优化晶粒尺寸分布,且Ga添加对Ce₁₇Fe₇₈B₆合金矫顽力的提升最为有效。研究发现,Ce₁₇Fe₇₈B₆合金回复曲线轻微开口;当Ga添加量为0.75 at.%时,合金具有较优异的综合磁性能,回复曲线完全闭合。适量Ga元素添加明显增强了Ce-Fe-B基合金晶间短程交换耦合作用,减小了合金平均回复磁导率,有效降低了Ce-Fe-B基合金在周期性反向磁场中的能量损失。     

Influence of the TbFe2 crystallization on the magnetic and magnetostrictive properties of (Fe3Ga/TbFe2)n heterostructures

In this work we have investigated (Fe₃Ga/TbFe₂)_n multilayers grown by sputtering at room temperature. These multilayers exhibit a large coercivity associated to the crystalline TbFe₂ Laves phase. To reduce the coercivity it is necessary to control the crystallization of that material. In this work, we focus on the analysis of the properties of the TbFe₂ layers. In the as-grown heterostructures we have found evidence of nanoaggregates in the TbFe₂ layers. The Fe₃Ga thickness and the thermal treatments have an influence on the volume of these nanoprecipitates. In the annealed samples, when increasing the Fe₃Ga thickness we observe a decrease in the nanoaggregate volume and thus in the coercivity. The experimental results indicate that the crystallization of the TbFe₂ depends on the Tb diffusion promoted by the thermal treatment and on the stiffness factor (Y/α) of the Fe₃Ga layer. The magnetostrictive properties are also strongly influenced by the crystallization of the TbFe₂. We have achieved a maximum magnetostriction constant of nearly 550 ppm with a coercive field close to 400 Oe.     

Effect of quenching on magnetostriction and microstructure of melt-spun Fe83Ga17 alloy

The effect of quenching on magnetostriction and microstructure of melt-spun Fe₈₃Ga₁₇ ribbons was investigated. The results show that magnetostriction of ribbons is greatly improved by heat treatment and the value of λ of ribbons reached nearly −2300 ppm after annealed at 700 °C for 3 h. The XRD analyses reveal that the microstructure of melt-spun Fe₈₃Ga₁₇ alloy ribbons was changed after heat treatment and the transition of A2 + DO₃ → A2 + DO₃ + DO₁₉ occurred at 700 °C for the ribbons. The magnetostriction of Fe₈₃Ga₁₇ ribbons is influenced by the emergence of DO₁₉ structure and the increase of ordered degree, and the variation of crystallinity of A2 phase is also related to the magnetostriction of Fe₈₃Ga₁₇ ribbons.     

Magnetic and magnetocaloric properties in melt-spun and annealed Ni42.7Mn40.8Co5.2Sn11.3 ribbons

The Ni_42.7Mn_40.8Co_5.2Sn_11.3 ribbons were prepared by melt spinning. After heat treatment, the martensitic transformation temperature and Curie temperature of austenite of the annealed ribbons increased remarkably. Inverse and direct magnetocaloric properties were investigated in the melt-spun and annealed ribbons. The effective refrigerant capacities for these ribbons were discussed in this paper.     

Cr含量对熔体快淬Al_(75-x)Si_(25)Cr_x锂离子电池合金负极电化学性能的影响(英文)

研究熔体快淬Al75-xSi25Crx(x=2,4,7,10,摩尔分数,%)锂离子电池合金负极材料的电化学性能。快淬带由纳米晶和非晶组成。电化学测试表明:负极材料存在活化过程;Al73Si25Cr2负极材料的最大比容量为1119mA·h/g,循环30次后可保持为586mA·h/g;Al71Si25Cr4合金的循环性能更加稳定,经过30次循环后,容量仅衰减24%;嵌Li极片中未检测到含Li的金属间化合物;退火后,由于惰性相Al13Si4Cr4的形成,合金的比容量减小,嵌Li极片中出现AlLi相;固溶于非平衡态合金中的Cr降低了嵌Li活性,增强了结构稳定性,这是活化和抑制结构演变的主要原因。     

Microstructure and magnetic properties of HVOF thermally sprayed Fe75Si15B10 coatings

Partially amorphous Fe₇₅Si₁₅B₁₀ coatings were prepared from nanostructured feedstock powders by using high velocity oxy-fuel spraying. Scanning electron microscopy, X-ray diffraction, Vickers indenter and magnetic measurements were used to investigate microstructural, structural, microhardness and magnetic properties of the coatings. The Rietveld refinement of the X-ray diffraction patterns reveals the presence of an amorphous phase, nanocrystalline α-Fe(Si,B) structure having a lattice parameter close to 0.2841 nm and an average crystallite size of about 78-83 nm in addition to small amounts of Fe₃O₄ oxide (104 nm) and Fe₂B boride (151 nm), which disappear completely with increasing coating thickness. Coercivity and microhardness values are 15.5 Oe and 478 Hv, respectively, for 84 μm thickness.