银基电接触材料的研究现状及发展趋势

从电接触材料的电学、力学和加工性能等要求出发,介绍了银基电接触材料的种类、特点、性能及研究进展。分析比较了常用银基合金(Ag-Ni系、Ag-W系和Ag-RE系)和银基氧化物(Ag-ZnO、Ag-CuO和Ag-SnO2)电接触材料的制备方法及优缺点。发展无公害环保型并能广泛适用的新型节银电接触材料,已成为目前银基电接触材料研究、应用的重点。     

新型银基电接触材料的研究进展

综述了3种新型银基电接触材料的性能特点。以NiO、Bi2O3或CuO改性的Ag/SnO2MeO可以改善传统Ag/SnO2电接触材料的接触电阻稳定性、温升控制及室温加工性;以Ag/Ti3SiC2和Ag/Ti3AlC2为代表的三元层状化合物陶瓷相增强银基材料(Ag/MAX)可以改善AgNi材料大电流条件下的抗熔焊性能,降低直流负载条件下材料转移量;用石墨烯替代传统石墨研制的Ag/GNPs可以解决表面膜增厚、接触电阻增大、耐磨性不足等缺点。提出新型银基电接触材料的主要研发方向。     

银基系列电接触复合材料的研发与应用

银基电接触复合材料具有优异的电接触性能,在低压电器、汽车电器和家用电器等行业有广泛的应用。从银基系列电接触复合材料的物理、力学、电学及加工性能等应用要求出发,介绍了银基系列电接触复合材料的制备方法、种类、性能、特点及应用领域,阐述了在已有的银基电接触材料中添加第三组元,改善银基系列电接触复合材料性能的情况。同时介绍了Ag-碳纳米管、Ag-导电陶瓷、Ag-石墨烯等新型银基电接触复合材料的性能、特点及应用领域。     

银基电接触材料的最新研究进展和展望

贵金属基电接触材料广泛应用于电子、电工行业,而Ag基电接触材料的用途和用量最大。总结了主要银基电接触材料中传统的Ag/Ni、Ag/CdO、Ag/SnO2、Ag/ZnO、Ag/C、Ag/W、Ag/WC材料,以及新型的Ag/CNT、Ag/Graphene、Ag/MAX材料的制备方法、性能、用途和研究现况。综述了近年来在电接触材料的实时原位测试技术,并对熔桥、电弧等现象的观测结果和技术进展,以及模拟仿真技术在电接触材料研究中对熔桥、电弧等研究成果和技术进展。分析了银基电接触材料研究中存在的问题,并展望了发展趋势。     

银基滑动电接触材料的研究进展

鉴于银基滑动电接触材料在微型电机、精密电子仪表等装置中的重要性,对此类材料的种类、制备工艺及研究进展进行了归纳与阐述。同时,分析了熔铸加工法、内氧化法、粉末冶金法等银基滑动电接触材料的制备工艺。结合现阶段研究工作,研发和改进制备工艺,加强基础理论研究、添加多组元进行材料改性是今后银基滑动电接触材料发展的主要方向。     

新型银稀土电接触材料的研究及应用

银基电接触材料具有优异的导电性和导热性,接触电阻低而稳定,加工性能优良,耐电弧熔焊和烧蚀,是低压电器、汽车电器和家用电器中广泛使用的电工材料。在银及银合金材料中添加稀土元素,可以抑制材料的自然时效和软化过程,提高材料的抗熔焊性、耐电弧烧蚀性、抗氧化能力以及力学性能,并且能够防止显微组织的长大,克服金属的迁移。阐述了稀土元素在银基电接触材料中的工作机制,以及银稀土新材料的应用情况。     

第二相粒度对AgSnO2 触头材料润湿性和电接触性能的影响

选用TiO₂作为触头材料的添加剂,采用粉末冶金法制备了6种不同第二相（SnO₂）粒度的AgSnO₂和AgSnO₂/TiO₂触头材料。研究了2种触头材料的润湿性和电接触性能。用座滴法测量了Ag与SnO₂之间的润湿角,并表征了材料的湿润性,使用JF04C电接触触头材料测试系统对材料电接触性能进行了测试,分析了不同第二相粒度的触头材料的润湿性和电接触性能的变化规律。结果表明,当第二相粒度为100~300 nm时,2种触头材料的性能均优于其它粒度的触头材料。     

AgSnO_2触头微观结构设计及电弧侵蚀模拟的进展

AgSnO_2作为一种无毒环保材料,因其优良的电接触性能而被广泛应用于低压开关和电源继电器领域。本文综述了近年来AgSnO_2触头材料的研发进展:在实验方面,分析比较了不同AgSnO_2电接触材料制备工艺的优缺点,介绍了AgSnO_2触头材料掺杂改性途径及其作用机理;在模拟方面,重点阐述了动、静触头电弧侵蚀过程以及触头微观结构演变行为,概述了基于第一性原理的触头掺杂体系的理论分析,介绍了考虑阳极蒸汽的真空电弧模拟研究。提出了结合实验和多尺度、多体系模拟来设计和研发新型AgSnO_2触头材料,对提高精密电气设备的可靠性和稳定性具有重要意义。     

环保型氧化物增强银基电接触功能复合材料研究进展

围绕研制开发具有与AgCdO性能相媲美的银基电接触材柞,报道柚近3年来传统Ag/SnO2、Ag/ZnO、Ag/CuO三种银基电接触材柞体系的研究现状,主要论述国内外研究恘者从掺杂改性、制备方法、材柞模拟仿真、第一性原理计算等方面开展的大柎优化研究;梳理柚目前制备银基电接触材柞体系的常规制备技术及其工作原理;简述柚当前部...     

Ag-SnO2电接触材料的研究进展及发展趋势

Ag-SnO2电接触材料因具有优良的物理性能、抗熔焊性和耐电弧烧蚀性等特性,已经成为最有可能代替传统有毒电接触材料Ag-CdO的一种新型环保电接触材料.基于40多篇文献的分析,归纳了包括合金内氧化法、粉末冶金法、喷涂法、模板法、磁控溅射法等制备工艺,增强相改性,增强相调控等方面对Ag-SnO2电接触材料组织性能的影响....     

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).     

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.     

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.     

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。