绝缘工程陶瓷的特种加工技术

针对用机械磨削方法加工绝缘工程陶瓷存在成本高、效率低和工件表面易产生微裂纹等问题，国内外学者开展了大量的研究工作，并取得了较大的研究进展。概述了绝缘工程陶瓷的激光加工、超声加工、电火花加工、等离子弧切割等特种加工技术，并对这些加工技术的原理、特点和应用状况等进行了分析评述。     

基于遗传算法的工程陶瓷电火花加工技术

工程陶瓷材料硬脆、导电率低,难以获得高效精密的电加工效果.本文针对工程陶瓷电火花加工特点,在分析国内外工程陶瓷电火花加工技术的基础上,提出了基于遗传算法的工程陶瓷电火花加工方法.该方法结合遗传算法、神经网络及模糊控制理论构造了多环式自适应控制系统,在线对加工过程进行断丝预防、加工工艺自适应和加工参数自适应监测与控制,从而为难加工材料实现高效精密的电火花加工提供理论与技术指导.     

超高温陶瓷不同型面加工方法的研究

针对超高温陶瓷材料及构件中一些典型型面的加工方法进行了研究,分别列举了深孔、螺纹及异形曲面等典型型面的加工方法和加工工艺,为超高温陶瓷的后续应用提供了技术保障。     

磨料水射流车削陶瓷材料的模型研究

工程陶瓷材料在航空航天等领域有着广泛的应用,由于工程陶瓷具有硬度大、脆性高、断裂韧性低等特点,其加工工艺性很差,极易产生细小裂纹和应力集中现象,影响陶瓷零件的综合性能及使用寿命。文章在研究磨料水射流单磨粒冲蚀机理的基础上,对氧化铝陶瓷材料应用磨料水射流进行车削加工,并建立车削陶瓷材料的深度模型。最后,进行磨料水射流车削实验,实验结果表明,该模型具有很高的可靠性。     

国内外先进陶瓷材料加工技术的进展

随着先进陶瓷材料的开发和应用,陶瓷材料的加工技术受到人们的普遍观注,本文查阅了近二十年来有关的文献资料,对国内外陶瓷材料加工技术的研究成果进行了系统地综述,并着重从材料的去除机理,优质高效加工新工艺及加工工艺装备三方面介绍了陶瓷材料的切削加工,磨削加工,研磨,抛光和孔加工技术的进展。     

钎焊连接陶瓷表面金属化的研究进展

先进结构陶瓷材料具有耐高温、高硬度、耐磨损、耐腐蚀等优良特性,但其加工性能很差,随着高性能陶瓷应用面的不断扩大以及现代高科技产业的发展对陶瓷材料性能提出了各种更为苛刻的要求,研究陶瓷材料的连接技术,特别是尺寸较大、形状复杂的陶瓷零部件的连接技术,是工程陶瓷制造与应用的关键技术之一。文中从工艺角度综述了陶瓷金属化的研究进展,重点介绍了陶瓷金属化的几种主要方法以及优缺点,提出了陶瓷金属化的研究方向。     

工程陶瓷磨削力的研究现状与进展

本文综述了近几年来国内外关于工程陶瓷磨削加工中磨削力的研究现状及进展，包括磨削力与陶瓷材料的显微结构及性能、磨削用量、机床刚度、磨削砂轮及磨削液的关系的研究。最后提出了在工程陶瓷磨削力方面，今后应重点开展的研究工作。     

钎焊金刚石薄壁钻加工工程陶瓷的试验研究

通过用钎焊金刚石薄壁钻加工Al2O3工程陶瓷的钻削试验，测量和分析了在不同加工参数下钻削轴向力和扭矩的变化，并与电镀钻头的加工性能进行了对比。结果表明，用钎焊金刚石薄壁钻加工工程陶瓷材料的设想可行，与电镀钻头相比，钎焊钻头钻削过程更稳定，加工质量更好，尤其在高转速、大进给加工条件下具有明显优势。     

工程陶瓷镜面磨削新方法及其机理的研究

基于各种磨削参数对氧化铝砂轮磨削氮化硅工程陶瓷材料表面粗糙度影响的试验研究，提出了氧化铝砂轮加工工程陶瓷时的作用过程可分为氧化铝砂粒与工件表面的凸峰碰撞破碎去除，碰撞与摩擦共同作用及摩擦抛光三个阶段，并建立了各阶段的去除模型。而后通过对不同磨削参数的工件加工表面进行微观观察，证明了上述加工机理的存在，并能获得良好的表面质量，达到了镜面加工要求，实现了在普通磨床上对陶瓷材料的高质量加工。     

国外工程陶瓷的精密加工

随着对工程陶瓷的深入研究和逐步获得应用,其精密加工成为需要解决的问题之一。本文简要评述了工程陶瓷的成形加工技术,包括热等静压、注射成形、切削加工及激光加工等。     

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。