Fe(Co)SiAl合金微粉的显微结构及电磁特性(英文)

铁基金属微粉广泛地用作吸波材料。用机械合金化的方法制备了Fe85Si9.6Al5.4和(Fe0.65Co0.35)85Si9.6Al5.4(质量分数,%)合金微粉。研究了球磨20和80h的微粉形貌,分析了微粉不同球磨时间的显微结构,测试了微粉在0.5～18GHz频段内的复数介电常数和复数磁导率,并计算了微波反射率。结果表明,球磨后微粉的粒径小于5μm,FeSiAl合金中硅和铝原子溶于铁原子的点阵中,同时,在FeCoSiAl合金中有FeSi和AlCo金属间化合物产生。在频率为8GHz附近,复数介电常数和复数磁导率匹配较好,此时FeCoSiAl合金微粉的最小反射率达到-13.7dB。     

纳米晶Fe85Si1Al6Cr8扁平状颗粒材料微波吸收特性

摘要采用雾化工艺和高能球磨处理技术制备纳米晶Fe85Si1Al6Cr8扁平状颗粒合金粉,研究了高能球磨处理工艺对材料微结构、形貌和微波电磁特性的影响．结果表明,高能球磨处理使球形雾化粉粒形状扁平化并细化其晶粒,从而使Fe85Si1Al6Cr8微粉的微波磁导率显著提高,有效控制了介电常数．后续热处理可以进一步改善其微波电磁性能．对采用该材料制作的涂层吸波性能进行的测量结果表明,在频率为4GHz附近微波段具有良好的吸波性能．     

退火热处理对扁平状Fe-Si-Al磁粉电磁性能的影响

采用搅拌球磨工艺对Fe-Si-Al粉末进行了扁平化处理,然后在不同温度及不同保温时间下对其进行了退火处理,借助激光粒度、SEM和XRD,研究了扁平化工艺和热处理工艺对Fe-Si-Al粉末粒度、形貌和物相组成的影响。借助阻抗分析仪,考察了以所制合金粉末为吸收剂制成的吸波材料在1MHz~100MHz频率范围内的电磁参数。结果表明:经扁平化和退火处理后,Fe-Si-Al吸波材料的复磁导率得到了显著提高,由经扁平化并经600℃退火2h的Fe-Si-Al粉末制成的吸波材料在1 MHz~100 MHz的低频段具有更加优异的电磁性能,起始磁导率实部达到64。     

MnAl粉体微波吸收特性的研究

采用电弧熔炼和高能球磨以及回火热处理工艺制备了Mn55Al45合金粉体,使用SEM、XRD和网络矢量分析仪分析了球磨时间和回火温度对Mn55Al45合金微粉的形貌、相结构及吸波性能的影响。结果表明：随球磨时间增加,粉体中Al2Mn3和Al11Mn14的相对含量会随之而增加;粉体的复介电常数虚部、复磁导率虚部的共振峰频率和吸收峰频率都随球磨时间的增加而逐渐向低频移动,球磨18 h的粉体有很好的频宽效果; 球磨24 h时,反射率峰值在16 GHz处达到 -28 dB。随回火温度的增加,粉体中的Al2Mn3增多,球磨 18 h后和 经400 ℃回火处理的粉体,在 6 GHz～ 18 GHz频段内有较好的综合吸波性能。在吸波涂层厚度d=2.0 mm 下, 400 ℃回火处理的粉体在17 GHz频率处具有最小反射率值为-26.4 dB。     

快淬Fe-Si-Al软磁合金的扁平化、微结构与电磁性能研究

用快淬法制备Fe-Si-Al合金薄带,通过高能球磨对其进行扁平化处理,在氮气保护下进行700 ℃退火处理30 min.研究了高能球磨工艺和退火处理对Fe-Si-Al合金样品形貌、结构及磁性能的影响.结果表明,高能球磨70 h后,Fe-Si-Al合金薄带细化为纵横比较大的扁平状微粉;后续的退火处理有效提高了合金样品的饱和磁化强度;利用退火态扁平化微粉制备的同轴圆环样品,在1 GHz附近具有良好的抗电磁干扰(EMI)特性.     

Dy和Al对Fe-Co合金微波吸收性能的影响

采用高真空电弧熔炼和高能球磨相结合的方法制备 Dy-Fe-Co 和 Dy-Fe-Co-Al合金微粉,利用X射线衍射技术（XRD）、扫描电镜分析方法（SEM）和矢量网络分析仪对合金粉的相结构、颗粒形貌和吸波性能进行分析。研究发现：随着Dy的添加,DyxFe90-xCo10(x=6, 9, 12)合金的吸收峰从低频向高频移动;在低频端,Dy6Fe84Co10合金的微波吸收性能优于其他合金,在d=1.8 mm厚度下,其吸收峰出现在3.6 GHz处,峰值达到 –6.7 dB;Al的适当添加可有效改善Fe-Co合金在低频端的微波吸收性能。在d=1.8 mm厚度下,Dy12Fe70Co10Al8合金的吸收峰在5.4 GHz处,峰值达到 –9.2 dB,在3~6 GHz频率范围内其微波吸收性能优于Dy12Fe78Co10合金     

扁平化Fe4N粉体的制备及其电磁性能研究

采用原料粉体扁平化后再氮化处理的方法制备了Fe4N扁平化粉体,并以石蜡作为粘结剂制备出粘结磁体,进而研究了球磨时间对粉体径厚比、比表面积以及粘结磁体的复磁导率等性能的影响。结果表明,制得的扁平化Fe4N粉体物相单一,径厚比大,厚度均匀,且小于计算得到的趋肤深度。采用扁平化Fe4N粉末制备的粘结磁体磁导率在一定频率范围内高于未处理粉末所制得的粘结磁体,但具有不同的频散特性。     

快淬Nd3Fe68Co18B11扁平粉粒微波电磁特性研究

本文研究了快淬Nd3Fe68Co18B11磁粉在不同球磨时间下的形貌、微结构和电磁特性.发现通过高能球磨能得到扁平状、大小趋于一致的小颗粒,同时细化晶粒,从而提高材料在微波低频段的磁导率、降低介电常数.基于传输线理论的数值模拟结果表明,所得磁性微粉在微波低频段具有良好的吸收性能.     

Nd2Fe14B／α-Fe复相材料微结构对微波复磁导率的影响

采用熔体快淬、晶化退火工艺及机械球磨方法制备了Nd2Fe14B／α-Fe纳米晶双相材料。研究了机械球磨工艺对材料的微结构、形貌和微波复磁导率的影响。结果表明：适当的机械球磨工艺可使材料粒度变细、变薄，晶粒细化，增强软、硬磁相晶粒间的交换耦合作用，提高其磁各向异性和饱和磁化强度，从而调节材料的共振吸收峰频率和微波复磁导率。球磨25h样品的复磁导率虚部μ’在3GHz达2．6，μ”在12GHz达1．2，μ”在30．5GHz达0．85，Nd2Fe14B／α-Fe纳米晶双相材料共振峰可控，不仅可应用于厘米波而且可应用于毫米波吸收材料的设计中。     

快淬Nd3Fe68Co18B11扁平粉粒微波电磁特性研究

本文研究了快淬Nd3Fe68Co18B11磁粉在不同球磨时间下的形貌、微结构和电磁特性。发现通过高能球磨能得到扁平状、大小趋于一致的小颗粒，同时细化晶粒，从而提高材料在微波低频段的磁导率、降低介电常数。基于传输线理论的数值模拟结果表明，所得磁性微粉在微波低频段具有良好的吸收性能。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。