Cu-Fe64Ni32Co4合金显微组织及热物理性能研究

本研究利用相图计算的CALPHAD方法和真空电弧熔炼技术,设计并制备了Cu_x(Fe_0.64Ni_0.32Co_0.04)_100-x(x=30, 45, 60, wt. %)系列合金。实验研究了该系列合金在不同热处理工艺时的显微组织,热导率以及热膨胀系数。研究结果表明：Cu-Fe₆₄Ni₃₂Co₄系列合金在600 °C和800 °C时效处理后均为fcc富铜相和fcc富因瓦(铁镍钴)相组成的各向同性的多晶合金。该系列合金在1000 °C淬火并在600 °C时效处理50 h后,其热膨胀系数变化范围为6.88~12.36×10_-6 K_-1;热导率变化范围为22.91~56.13 W.m_-1.K_-1;其热导率明显高于因瓦合金,其中Cu₃₀(Fe_0.64Ni_0.32Co_0.04)₇₀与 Cu₄₅(Fe_0.64Ni_0.32Co_0.04)₅₅合金的热膨胀系数可以与电子封装中半导体材料的热膨胀系数相匹配。     

Anisotropy compensation and high low-field magnetostriction of epoxy/Tb1−xHox(Fe0.8Co0.2)2 composites (0.60 ≤ x ≤ 1.0)

The anisotropy compensation and magnetostrictive properties of Tb_1−xHo_x(Fe_0.8Co_0.2)₂ (0.60 ≤ x ≤ 1.0) alloys have been investigated. The easy magnetization direction (EMD) at room temperature rotates from the 〈1 1 1〉 axis (x ≤ 0.75) to the 〈1 0 0〉 axis (x ≥ 0.90) through an intermediate state 〈1 1 0〉, subjected to the anisotropy compensation between Tb³⁺ and Ho³⁺ ions. Composition anisotropy compensation is realized near x = 0.75. The Tb_0.25Ho_0.75(Fe_0.8Co_0.2)₂ alloy has a minimum anisotropy and a large spontaneous magnetostriction coefficient λ₁₁₁ (≈740 ppm) at room temperature. The strong 〈1 1 1〉-oriented 1-3 epoxy-bonded composite has been fabricated by curing under a moderate magnetic field. A high low-field magnetostriction of about 400 ppm at 3 kOe is obtained for the 1-3 epoxy/Tb_0.25Ho_0.75(Fe_0.8Co_0.2)₂ composite with 40-vol% alloy particles, which can be attributed to the low magnetic anisotropy, EMD lying along 〈1 1 1〉 direction, the strong 〈1 1 1〉-textured orientation and the chain structure.     

Hf、CNTs混合掺杂对纳米晶Sm5Co19合金结构和磁性能的影响

对制备出纳米晶组织的Sm_5Co_(19)Hf_(0.4)合金和Sm_5Co_(19)Hf_(0.4)CNTs_(0.4)合金的显微组织、晶体结构和磁性能等进行了系统表征分析。结果表明:Hf元素和碳纳米管(CNTs)的混合添加不引起Sm_5Co_(19)合金Ce_5Co_(19)型结构发生相分解,且使纳米晶组织中的晶粒变得细小,晶粒尺寸均匀分布。能谱分析表明,添加的CNTs进入纳米晶Sm_5Co_(19)Hf_(0.4)CNTs_(0.4)合金的晶界区域,产生晶界钉扎作用,显著提高纳米晶Sm_5Co_(19)合金的矫顽力。晶体结构精修表明,Hf元素进入纳米晶Sm_5Co_(19)合金晶胞结构的Sm空位,导致晶格参数a、b、c均减小,而轴比c/a增加,使Hf掺杂的纳米晶合金的磁晶各向异性增大,具有提高纳米晶合金的矫顽力的作用。本研究结果对设计制备具有高磁晶各向异性、高内禀矫顽力的Sm-Co基合金具有明确指导意义。     

Magnetoresistive sensitivity and uniaxial anisotropy of spin-valve microstrips with a synthetic antiferromagnet

Microobjects (strips) were formed by contact photolithography using Та/Ni₈₀Fe₂₀/Co₉₀Fe₁₀/Cu/Co₉₀Fe₁₀/Ru/Co₉₀Fe₁₀/Fe₅₀Mn₅₀/Ta spin-valves prepared by magnetron sputtering. A mutually perpendicular arrangement of uniaxial and unidirectional anisotropy axes in microobjects has been formed using two different thermomagnetic treatment regimes. The magnetoresistive sensitivity of spin valve and spin-valve-based microobject has been found to depend on the mutual arrangement of the easy magnetization axis and direction of magnetic field applied upon thermomagnetic treatment. The obtained data have been interpreted taking into account changes in the induced anisotropy and anisotropy due to the shape of the microobject.     

Superelastic behavior of nanostructured Ti50Ni48Co2 shape memory alloy with cold rolling processing

Effects of cold rolling followed by annealing on microstructural evolution and superelastic properties of the Ti₅₀Ni₄₈Co₂ shape memory alloy were investigated. Results showed that during cold rolling, the alloy microstructure evolved through six basic stages including stress-induced martensite transformation and plastic deformation of martensite, deformation twinning, accumulation of dislocations along twin and variant boundaries in martensite, nanocrystallization, amorphization and reverse transformation of martensite to austenite. After annealing at 400 °C for 1 h, the amorphous phase formed in the cold-rolled specimens was completely crystallized and an entirely nanocrystalline structure was achieved. The value of stress level of the upper plateau in this nanocrystalline alloy was measured as high as 730 MPa which was significantly higher than that of the coarse-grained Ni₅₀Ti₅₀ and Ti₅₀Ni₄₈Co₂ alloys. Moreover, the nanocrystalline Ti₅₀Ni₄₈Co₂ alloy had a high damping capacity and considerable efficiency for energy storage.     

Structural, microstructural and magnetic properties of amorphous/nanocrystalline Ni63Fe13Mo4Nb20 powders prepared by mechanical alloying

This paper focuses on the magnetic, structural and microstructural studies of amorphous/nanocrystalline Ni₆₃Fe₁₃Mo₄Nb₂₀ powders prepared by mechanical alloying. The ball-milling of Ni, Fe, Mo and Nb powders leads to alloying the element powders, the nanocrystalline and an amorphization matrix with Mo element up to 120 h followed by the strain and thermal-induced nucleation of a single nanocrystalline Ni-based phase from the amorphous matrix at 190 h. The results showed that the saturation magnetization decreases as a result of the electronic interactions between magnetic and non-magnetic elements and finally increases by the partial crystallization of the amorphous matrix. The coercive force increases as the milling time increases and finally decreases due to sub-grains formation.     

MAGNETOMECHANICAL DAMPING CAPACITY OF <110> ORIENTED Tb0.36Dy0.64(Fe0.85Co0.15)2 ALLOY

采用区熔定向凝固方法, 以480 mm/h速度制备了<110>取向Tb_0.36Dy_0.64(Fe_0.85Co_0.15)₂合金棒. 通过测试在0---0.325 T磁场范围内合金 棒的应力--应变回线, 计算了应力幅σ_m分别为-10,-30和-50 MPa的阻尼系数Δ W/W. 结果表明, 零磁场下的Δ W/W最大; 随磁场强度增大, 同一σ_m条件下的Δ W/W逐渐降低. 在低磁场中, Δ W/W随σ_m的增加而降低; 在高磁场中,  Δ W/W随σ_m的增加而升高. 利用不同预压应力下的磁致伸缩--磁化强度关系曲线, 分析了磁场--应力复合加载条件下非180°磁畴和畴壁的运动形式. 依据局部内应力理论, 解释了合金棒的磁机械阻尼系数随外磁场强度和应力幅值变化的规律.     

Effect of Co addition on the magnetic properties of nanocrystalline Fe-rich Fe-Nb-(Nd,Pr)-B alloys produced by crystallization of an amorphous phase

The effect of Co addition on the magnetic properties and microstructure for the nanocrystalline Fe_93-xNb₂(Nd,Pr)₂B₂ (x = 5–7) alloys produced by crystallization of an amorphous phase has been investigated. The melt-spun Fe_93-x-yCo_xNb₂(Nd,Pr)_yB₅ (x = 0–20 and y = 5–7 at.%) ribbons form a nanocomposite structure of bcc-(Fe,Co) and Pr₂(Fe,Co)₁₄B with grain sizes of 10–50 nm after annealing at 973-1023 K, showing a smooth J-H curve typical for the exchange-spring magnet. The alloys containing Co show a high energy product ((BH)_max) upon annealing at a relatively low temperature presumably because the precipitation temperature of each phase decreases by addition of CO. The (BH)_max values after annealing at an optimum temperature are improved by addition of 5–20 at. % Co for the Fe_86-xCo_xNb₂(Nd,Pr)₇B₅ and Fe_88-xCo_xNb₂Nd₅B₅ alloys. The improvement of (BH)_max by Co addition is attributed to the enhancement of J_r, presumably resulting from the increase in magnetization of each phase and the exchange-coupled region between the soft and hard magnetic phases.     

Soft magnetic Fe25Co25Ni25(B,Si)25 high entropy bulk metallic glasses

New Fe₂₅Co₂₅Ni₂₅(B, Si)₂₅ high entropy bulk metallic glasses (HE-BMGs) with superior soft magnetic and mechanical properties are developed. The HE-BMGs show high glass transition temperature and wide supercooled liquid region (ΔT_x). Fully glassy rods with diameters up to 1.5 mm were fabricated for the Fe₂₅Co₂₅Ni₂₅(B_0.7Si_0.3)₂₅ alloy by copper mold casting method. The HE-BMGs exhibit high yield strength of ∼3624 MPa with large plastic strain of ∼3.1%, which is superior to the pre-developed HE-BMGs. The alloys also possess good soft magnetic properties, i.e., rather high saturation magnetization of ∼0.87 T, low coercive force of ∼1.1 A/m, and high effective permeability at 1 kHz of ∼19,800. This combination of these excellent properties gives the new HE-BMGs good promise for both scientific and engineering applications.     

Effect of the structure and thickness of layers on the magnetic and magnetoresistive properties of <Emphasis Type="Italic">Py</Emphasis>/Co/Cu/Co nanocrystalline films

Py/Co₁/Cu/Co₂ films (Py is the Ni₆₃Co₂₅Fe₁₂ ternary permalloy) were produced by magnetron sputtering on glass substrates. The thicknesses of layers are d _Cu = 0.7–4 nm, \(d_{Co_2 } \) = 2–12 nm, and d _Py = 2–12 nm. The polar diagrams of the films with d _Cu = 1.2nm demonstrate a biaxial anisotropy, whereas the films with 2.0 ≤ d _Cu ≤ 3.0 nm are characterized by uniaxial anisotropy. The first maximum in the Δρ/ρ = f(d _Cu) curve is due to an antiferromagnetic coupling between the Py/Co₁ and Co₂ layers; the second maximum is due to the independent magnetization reversal of the Py/Co₁ soft magnetic bilayer and Co₂ hard magnetic layer. The magnetoresistance measured along the EA exhibits an almost twofold increase with increasing thickness of ferromagnetic layers. The coercive force was shown to decrease with increasing thickness of the Co₂ layer, whereas the magnetic anisotropy field is unchanged. The coercive force and induced magnetic anisotropy were estimated theoretically taking into account changes in the mean-square amplitude and roughness period with increasing thickness of the Co₂ layer. The results obtained agree with experimental data.     

Fe掺BaZrS3磁性半导体的制备与研究

硫族钙钛矿是一类新兴的半导体功能材料,具有独特的电子结构与光电性质。本文采用溶胶-凝胶法结合化学气相反应的方法制备了硫族钙钛矿BaZrS₃纳米结构,并且借助掺杂的方法获得了BaZr_1-xFe_xS₃磁性半导体,并对其结构和光、磁学等性能进行研究。结果表明,对氧化物钙钛矿BaZrO₃进行硫化处理,即用同族的S元素替代O元素,样品仍然可以表现出钙钛矿结构,而且硫化处理可以起到降低带隙宽度的作用。同时用具有局域磁矩的3d过渡族金属元素,如Fe进行钙钛矿B位阳离子掺杂,通过控制Fe的掺杂量同样可以系统地调控样品的带隙宽度,而且对于BaZr_99.7Fe_0.03S₃和BaZr_99.5Fe_0.05S₃样品表现出了室温铁磁性。     

Magnetic, electrical and plastic properties of Fe76Nb2Si13B9, Fe75Ag1Nb2Si13B9 and Fe75Cu1Nb2Si13B9 amorphous alloys

Influence of 1 h annealing in vacuum on magnetic, electrical and plastic properties of Fe₇₆Nb₂Si₁₃B₉, Fe₇₅Ag₁Nb₂Si₁₃B₉ and Fe₇₅Cu₁Nb₂Si₁₃B₉ melt spun ribbons were carefully investigated. It was shown that in all cases soft magnetic properties can be significantly enhanced by applying 1-h annealing at characteristic temperatures T_op. This optimization annealing causes that permeability increases more than 15-times and magnetic losses (tangent of loss angle) achieves a minimum in relation to the as quenched state. Using structural examinations (X-ray and HRTEM) it was shown that for the Fe₇₅Cu₁Nb₂Si₁₃B₉ alloy the optimized microstructure corresponds to a nanocrystalline αFe(Si) phase whereas in other alloys to a relaxed amorphous phase free of iron nanograins. As a consequence of this fact the Fe₇₆Nb₂Si₁₃B₉ and Fe₇₅Ag₁Nb₂Si₁₃B₉ alloys show higher plasticity in comparison to the nanocrystalline Fe₇₅Cu₁Nb₂Si₁₃B₉ alloy. Temperatures of the first stage of crystallization, and related diffusion parameters were determined using measurements of resistivity versus temperature with different heating rates.     

Magnetic anisotropy of Ho–Fe–Co–Cr intermetallic compounds

Starting with a Ho₃(Fe_1−xCo_x)_29−yCr_y, (x,y) = (0.6,4.5) and (0.8,5.5) nominal stoichiometry, a disordered variant of the hexagonal 2:17 phase (Th₂Ni₁₇-type, S.G. P6₃/mmc) occurs, since both the monoclinic 3:29 and the transition-metal-rich disordered Th₂Ni₁₇-type hexagonal compounds have the same rare earth to transition metal ratio, 1:9.7. The magnetic properties and the magnetocrystalline anisotropy of these compounds have been investigated. The anisotropy constant, K's, and the anisotropy field, μ₀H_A, values have been deduced from the magnetization curves measured on powder samples magnetically aligned in a rotating magnetic field. The compound with (x,y) = (0.8,5.5) shows a compensation point at about 55 K. The magnetic anisotropy of both compounds is that of easy-plane from room temperature to low temperatures down to 5 K.     

High-field magnetization of a Dy2Fe14Si3 single crystal

The magnetization of a Dy₂Fe₁₄Si₃ single crystal was measured at 4.2 K in pulsed fields up to 51 T along the principal axes. The compound orders ferrimagnetically at 500 K, has a spontaneous magnetic moment of 8 μ_B/f.u. (at 4.2 K) and exhibits a very large magnetic anisotropy, 〈1 0 0〉 being the easy axis. In fields applied along the 〈1 0 0〉 and 〈1 2 0〉 axes, field-induced phase transitions are observed at 33 T and at 39 T, respectively. The c-axis magnetization curve crosses the easy-axis curve at 19 T. At higher fields, for all directions, the magnetization continues to increase due to further bending of the sublattice moments. Temperature evolution of magnetic anisotropy and magnetic hysteresis are discussed as well.     

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.     

Effect of rapid quenching on the microstructure and electrochemical characteristics of La_（0.6）Ce_（0.4）Ni_（3.6）Co_（0.65）Mn_（0.4）Al_（0.2）Ti_（0.05_（FeB）_（0.1） hydrogen storage alloy

In order to improve the cycling stability of AB₅ type alloy electrodes, rapid quenching technology and new alloy composition design were employed. A hydrogen storage alloy with nominal composition La_0.6Ce_0.4Ni_3.6Co_0.65Mn_0.4Al_0.2Ti_0.05(FeB)_0.1 was prepared by vacuum magnetic levitation melting under high purity argon atmosphere, followed by rapid quenching at different cooling rates. XRD results show that all alloys exhibit the single-phase CaCu₅-type structure. Electrochemical tests indicate that rapid quenching can slightly improve the cycling life of the alloy. Nevertheless, the high-rate dischargeability of the quenched alloys is lower than that of the as-cast alloy.     

Nitrided and carbided magnets

In this article, we review our recent studies on new rare-earth intermetallic compounds including the Ga, Si substituted 2:17-type compounds, their nitrides, carbides, and the Sm₃ (Fe,Ti)₂₉N₅ compounds. Much of our recent work is focused on the Sm₂(Fe,Ga)₁₇C_x alloys where we used melt spinning and subsequent annealing to obtain high coercivity. The highest coercivity obtained so far was in Sm₂Fe₁₄Ga₃C_2.5 with a value of 12.8 kOe at room temperature. The off-stoichiometric Sm₂Fe_14-xCo_xSi₂N_y nitrides maintain the Th₂Zn₁₇-type structure but with a unit-cell expansion ΔVV up to 5 % compared to the host materials. The Sm₂Fe_14-xCo_xSi₂C_z carbides maintain the Tr₂Zn₁₇-type structure when z = 1 and transform to the BaCd₁₁-type structure when z = 2. A very large anisotropy field with an applied magnetic field (H_a) value of 227 kOe for Sm₂Fe₁₄Si₂N_2.6 and 276 kOe for Sm₂Fe₁₀Co₄Si₂N_2.3 is observed at low temperature (1.5 K). The Sm₃(Fe,Ti)₂₉N₅ compound and its nitrides show very interesting magnetic properties. Both of these compounds exhibit ferromagnetic ordering with Curie temperature (T_c) of 486 and 750 K, respectively. The room temperature saturation magnetization is 119 emu/g for the parent compounds and 145 emu/g for the nitrides. The easy magnetization direction changes from planar to uniaxial upon nitrogenation. The anisotropy field for the nitrides is 12 T at room temperature and 25 T at 4.2 K.     

Preparation of Ni0.5Zn0.5Fe2O4/SiO2 nanocomposites and their adsorption of bovine serum albumin

The magnetic nanocomposites of (1 − x)Ni_0.5Zn_0.5Fe₂O₄/xSiO₂ (x = 0-0.2) were synthesized by the citrate-gel process and their absorption behavior of bovine serum albumin (BSA) was investigated by UV spectroscopy at room temperature. The gel precursor and resultant nanocomposites were characterized by FTIR, XRD, TEM and BET techniques. The results show that the single ferrite phase of Ni_0.5Zn_0.5Fe₂O₄ is formed at 400 °C, with high saturation magnetization and small coercivity. A porous, amorphous silica layer is located at the ferrite nanograin boundaries, with the silica content increasing from 0 to 0.20, the average grain size of Ni_0.5Zn_0.5Fe₂O₄ calcined at 400 °C reduced from about 18-8 nm. Consequently, the specific surface area of the nanocomposites ascends clearly with the increase of silica content, which is largely contributed by the increase in the thickness of the porous silica layer. The Ni_0.5Zn_0.5Fe₂O₄/SiO₂ nanocomposites demonstrate a better adsorption capability than the bare Ni_0.5Zn_0.5Fe₂O₄ nanoparticles for BSA. With the increase of the silica content from 0 to 0.05 and the specific surface area from about 49-57 m²/g, the BSA adsorption capability of the Ni_0.5Zn_0.5Fe₂O₄/SiO₂ nanocomposites calcined at 400 °C improve dramatically from 22 to 49 mg/g. However, with a further increase of the silica content from 0.05 to 0.2, the specific surface area increase from about 57-120 m²/g, the BSA adsorption for the nanocomposites remains around 49 mg/g, owing to the pores in the porous silica layer which are too small to let the BSA protein molecules in.     

Magnetic properties of (Fe)1−x–(Al2O3)x and (Fe50Ni50)1−x–(Al2O3)x nanocomposite magnetic media synthesized using gel like Al2O3 matrix

Composites with ferromagnetic nanoparticles, Fe and Fe₅₀Ni₅₀, dispersed in Al₂O₃ have been synthesized by a solution phase technique. The structure and magnetic properties of these composites with varying fractions of Al₂O₃ have been investigated. Both Fe and Fe₅₀Ni₅₀ nanoparticles are amorphous in the as-prepared state and become crystalline on heat treating with near equilibrium lattice parameters of 0.287 nm and 0.358 nm respectively. The interparticle distance increases with increasing Al₂O₃ from 0 wt.% to 20 wt.%. The size of Fe nanoparticles is 40 nm while the Fe₅₀Ni₅₀ nanoparticles are 20 nm in size. The Fe and Fe₅₀Ni₅₀ nanoparticles dispersed composites are found to be ferromagnetic at room temperature both in the as-prepared and heat treated conditions with clear coercive fields of 5.5–35 × 10³ A m⁻¹. The saturation magnetization increases by orders of magnitude on heat treatment, for e.g. from <1.0 emu g⁻¹ to 143.4 emu g⁻¹ for Fe–15 wt.% Al₂O₃ and 95.6 emu g⁻¹ for Fe₅₀Ni₅₀–15 wt.% Al₂O₃. The Fe-composites exhibit a Curie transition at 1000 K while the Fe₅₀Ni₅₀ composites exhibit a transition at 880 K, both temperatures close to bulk values.     

Fe- and co-based nanocrystalline soft magnetic alloys modified with Hf, Mo, and Zr: Magnetic properties, thermal stability, and structure. Alloys (Fe0.6Co0.4)86Hf7B6Cu1 and (Fe0.7Co0.3)88Hf7B4Cu1

Nanocrystalline alloys (Fe_0.6Co_0.4)₈₆Hf₇B₆Cu₁ and (Fe_0.7Co_0.3)₈₈Hf₇B₄Cu₁ have been investigated to obtain materials with improved thermal stability and new features. In order to make the alloys produced by melt quenching on a rotating wheel nanocrystalline, they have been subjected to heat (HT) and thermomechanical (TMechT) treatments. The effect of HT and TMechT conditions on the magnetic properties, thermal stability, and structure of the alloys has been studied. The optimal HT conditions for obtaining the minimum values of the coercive force (H _c) in the alloys have been determined. It is shown that TMechT of the alloys leads to the induced longitudinal magnetic anisotropy with the axis of easy magnetization along the long side of the ribbon in the studied temperature range of 520–620°C. It has been established that the alloys (Fe_0.6Co_0.4)₈₆Hf₇B₆Cu₁ and (Fe_0.7Co_0.3)₈₈Hf₇B₄Cu₁ are thermally unstable at temperatures above 500°C.