真空钎焊非接触式引弧特性研究

介绍了真空电弧钎焊设备的组成及特点。以理论与试验研究相结合的方法对真空电弧钎焊技术引弧过程的特性进行了研究,分析了引弧过程中各影响因素对电弧建立的影响,并通过试验对理论分析进行了验证。结果表明,在引弧过程中,引弧电压在大于最小引弧电压的情况下,引弧电压越大、真空度越低,钽管直径在不易烧断的情况下直径越小,电弧越易建立。     

磁控电弧焊接工艺在非熔化极气体保护焊中的应用

针对非熔化极气体保护焊,介绍了作用于焊接过程中的平行磁场、横向磁场、纵向磁场、双尖角磁场和旋转磁场的特点及磁场发生装置的组成,分析了磁偏弧工艺、磁摆弧工艺、均匀纵向磁场作用下的磁旋弧工艺、非均匀纵向磁场作用下的磁旋弧工艺、旋转磁场作用下的磁旋弧工艺、磁再压缩技术等国内外典型的磁控电弧焊接工艺的基本原理、应用范围及存在的问题.并对焊接电弧外形的变化和运行机制,焊接电弧外加磁场强度的变化关系进行了研究.     

节流孔直径和分布对静压气浮主轴稳态性能的影响

采用有限元法求解静压气浮主轴内气体流动雷诺方程，计算主轴承载能力、刚度和高度角等稳态性能，研究平均气膜厚度、偏心率、转速不同时直径系数(相邻节流孔直径比)和分布系数(相邻节流孔间隔比)对主轴稳态性能的影响。结果表明：直径系数减小或分布系数增大，承载能力和刚度增大而高度角减小；直径系数和分布系数不变，增大平均气膜厚度，承载能力和刚度减小，高度角先减小后增大；偏心率越大，承载能力越大，刚度越小；转速增加，高度角增大。较小的直径系数和较大的分布系数有利于提高主轴承载能力和刚度，降低高度角；较小的平均气膜厚度有利于提高主轴的承载能力和刚度，较大的偏心率主轴承载能力提高而刚度降低。     

TC4钛合金薄板等离子弧开槽堆焊工艺探究

采用微束等离子弧焊接方式对开槽TC4薄板进行了堆焊试验,以模拟TC4薄壁零件遭受刮削损伤时的焊接修复过程。分析研究了等离子弧焊接工艺参数对堆焊接头成形的影响,对最优工艺焊接的接头进行系列的性能测试。试验结果表明,送丝速度一定时,焊接电流越大,堆焊接头熔合区的高度越低,熔合区下垂部分越大;焊接电流一定时,送丝速度越大,则熔合区高度越高;大焊接电流下,送丝速度越大,则接头的熔合区越宽,热影响区也越宽,而小焊接电流下,随着送丝速度的提高,熔合区宽度变化较小,热影响区变窄。优化工艺后的焊接接头相对于母材抗拉强度更高,塑性稍差。焊缝缺口拉伸试样的断口在熔合区,断裂方式为准解理断裂。     

横向交变磁场作用下的等离子体弧特性分析

以外加横向交变磁场作用下的等离子体弧为研究对象,建立了等离子体弧摆动幅度和热流密度分布的数学模型.对横向交变磁约束下的等离子体弧射流特性进行理论研究,并分析工艺参数和励磁强度对横向交变磁约束等离子体弧形态和特性的影响规律.结果表明,横向交变磁场可有效控制等离子体弧形态和位置,等离子体弧在横向交变磁场作用下,分布范围增大、热流密度梯度减小.其摆动幅度随磁场强度的增加而增大,但过高的磁场强度会使等离子体弧变得不稳定;相同励磁强度下,气流量和弧电流越小、喷嘴到工件的距离越大,则摆动幅度越大;而工件表面的等离子体弧热流密度分布随励磁强度的增强趋于平坦化;相同励磁条件下,热流密度峰值随气体流量和弧电流的增大而增大、随喷嘴到工件距离的增大而减小.     

柴油机电控柱塞泵的多物理场耦合分析

为精确预测在高压环境下柱塞腔内多物理场耦合作用对燃油喷射系统供油过程的影响,基于柱塞腔、柱塞副泄漏、燃油物理特性等模型建立热-流-固多物理场耦合模型。通过解耦计算和试验方法验证该模型具有较高的精度。数值分析结果表明：柱塞直径越大,残余容积越小,柱塞腔内燃油压力升高率越大;增大柱塞副初始密封长度、减小初始柱塞副间隙或者增加凸轮转速时,由于柱塞副泄漏量较少,对供油过程压力特性的影响较小;燃油初始温度越低,燃油的体积弹性模量和密度越大,导致柱塞腔内燃油压力升高率较快。     

同轴送粉工艺参数对激光增材再制造喷嘴粉流流场的影响规律

激光增材再制造同轴送粉喷嘴粉流汇聚特性是影响零件成形质量和成形效率的重要因素,基于 DEM-CFD 耦合方法,开展三维同轴送粉喷嘴粉-气流场仿真分析,依据表征粉流汇聚特性的喷嘴中心轴向粉流分布浓度、焦点距离、 上焦点截面粉流分布浓度和单位距离粉流分布浓度等参数,设计单因素试验,在喷嘴结构不变的条件下,分析输粉气流速度、送粉速率和中心光路保护气速度对粉流分布的影响规律。 结果表明:输粉气流速度越大,焦点距离越小,轴向粉流分布浓度越小,上焦点截面粉流浓度分布直径越小,单位距离粉流分布浓度越大,粉流的集聚性越好;中心光路保护气速度对粉流焦点浓度影响较小,保护气速度越大,焦点距离越大,上焦点截面粉流浓度分布直径越小,单位距离粉流分布浓度增加,粉流的集聚性越好;送粉速率对焦点距离影响较小,送粉速率越大,喷嘴轴向粉流分布浓度越大,上焦点截面粉流浓度分布直径越大,单位距离粉流分布浓度出现先增大后减小的趋势。     

磁控等离子体弧金属板件柔性成形技术研究

等离子体弧柔性成形技术（FFUPA）是近年来发展起来的金属板件成形技术．利用该技术得到表面光滑、弯曲曲率小的工件较困难。为解决此关键技术问题,由等离子体的“与磁场可作用性”这一特点,利用低强度的均匀磁场来控制电子运动和增加在等离子体系统（磁控装置）中电子运动路径的长度,分散单位时间内单位面积上的等离子体数量,从而得到表面较光滑、弯曲曲率较小的工件。通过交变磁场再约束等离子体弧柔性成形实验,研究了等离子体弧在交变磁场中的特性,分析了加入交变磁场对板件弯曲成形表面质量、弯曲成形速度的影响规律。     

冲击装置对磁脉冲冲击介质成形的影响

针对冲击装置结构，探究底部直径、台阶直径、锥体底角等参数变化对其几何结构的影响。利用有限元仿真方法，考虑材料高应变速率和介质超弹性本构关系，建立磁场和变形场模型，分析冲击装置的结构参数对成形高度、应变速率和冲击速度的影响。结果表明：随底部直径减小，板材的成形高度和冲击装置的冲击速度增加，无台阶与小台阶下的成形高度接近，板材中心第1个应变速率峰值增加；台阶直径减小，更有利于提高冲击装置的冲击速度，提升成形高度；底部直径一定时，板材的成形高度随着锥体底角的减小趋于增加；底部直径减小到一定程度时，锥体底角对成形高度的影响不明显。     

铜箔电磁辅助微冲孔试验

为实现铜箔微冲孔,以弹性体作为传力介质,采用试验方法研究弹性介质材料、厚度及驱动片厚度等参数对电磁辅助微冲孔的影响。结果表明,硅胶和聚氨酯橡胶适合于电磁辅助微冲孔,最佳厚度分别为3.0mm和1.0mm;驱动片厚度对磁场渗透和运动速度有较大影响。板料厚度相同时,微孔直径越小冲孔越困难,需要的能量越大;板料厚度越薄,相同能量下可冲出直径越小的孔;通过合理控制工艺参数,电磁辅助成形技术可在20μm的铜箔上冲出直径500μm的微孔。     

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。