基于中间过渡层的5A06/0Cr18Ni10Ti气化冲击焊接工艺研究

利用气化冲击焊接技术,制备了力学性能良好基于中间层的5A06铝合金与0Cr18Ni10Ti不锈钢气化冲击焊接接头,中间层3003铝合金与飞板5A06铝合金和靶板0Cr18Ni10Ti界面焊接良好,接头结合区域呈圆环状。通过信号采集系统分析了铝箔气化时间和电流随能量输入的变化,采用OM和SEM分析了接头界面的微观形貌和元素分布。研究了能量输入对铝箔气化的时刻和接头力学性能的影响。结果表明,随着能量输入的增加,铝箔气化所需时间减小,最终碰撞速率增大,从而使焊接区域直径增大;接头的抗拉力和抗剪力随能量输入的增大而增大。当能量输入为9 kJ时,接头的最大抗拉力为44.0 k N,抗剪力为2.1 kN;5A06/3003界面呈中间对称波状结合,3003/0Cr18Ni10Ti界面以金属间化合物连接,结合区域错位分布。     

5182Al/HC340LA异种金属件磁脉冲焊接数值模拟与试验验证

采用顺序耦合法建立了三维电磁场和变形场的仿真模型。采用Ls-dyna将有限元方法和边界元方法相结合,对5182Al/HC340LA板件磁脉冲焊接过程进行仿真模拟。通过分析仿真模型的电磁场和变形场,发现飞板的感应电流和电磁力出现了双波峰的现象并且感应电流在飞板的搭接区域形成了两个相连的矩形回路。放电能量是磁脉冲焊接过程中一个重要的工艺参数,随着放电能量的增加,飞板的感应电流、电磁力、板件塑性变形、碰撞速度也随之增加。开展不同放电能量下的磁脉冲焊接工艺试验,通过对比飞板的速度和变形量,发现试验结果与数值模拟结果吻合较好,验证了该数值模型的可靠性。     

不同热输入条件下Q345E低合金钢焊接过热区的组织和冲击性能

采用焊接热模拟技术对Q345E低合金钢在不同焊接热输入下过热区的组织和冲击性能进行研究。结果表明:随着焊接热输入的增加,过热区组织由先共析铁素体+珠光体及部分马氏体逐渐转变为粒状贝氏体和针状铁素体组织,当焊接热输入达到3.06 kJ/mm时,出现少量魏氏组织,冲击功最低;随着焊接热输入增加,粗晶区的平均硬度值逐渐降低;当焊接热输入为1.35 J/mm时,显微组织中出现少量的板条马氏体,硬度最高;而当焊接热输入达到2.68kJ/mm时,显微组织中出现针状铁素体,硬度下降较明显;冲击功整体呈现逐渐降低趋势,焊接热输入为2.68 kJ/mm时,冲击功最大。     

热输入对高强耐候钢FCAW接头组织和性能的影响

在三种热输入下进行了高强耐候钢药芯焊丝电弧焊,利用光学显微镜和扫描电镜分析了焊缝和热影响区组织,并对焊接接头的强度、硬度和-40°冲击吸收能量进行了分析。结果表明,三种热输入下,焊缝组织主要以针状铁素体为主,热影响区组织均为板条贝氏体加粒状贝氏体,并且随热输入增大,焊缝和热影响区组织有一定粗化。在小热输入0. 74 kJ/mm和中等热输入0. 96 kJ/mm下,焊缝金属的强度和塑性与母材相当;在大热输入1. 19 kJ/mm下,焊缝位置发生了脆化。在三种热输入下,焊接热影响区的冲击吸收能量均低于焊缝区,焊缝和热影响区均为韧/脆混合断裂模式。     

热输入对工程机械用高强钢焊接接头组织和性能的影响

采用富Ar气体保护焊方法,使用φ1.6mm的MK.GHS80实芯气保焊丝对板厚为20 mm的HG785D钢进行对接焊,对焊接接头显微组织进行了观察,并对接头拉伸、弯曲、冲击等力学性能进行了检测,研究了热输入对焊接接头组织和性能的影响。结果表明,焊缝组织主要为针状铁素体+少量先共析铁素体,随着热输入的增加,焊缝中先共析铁素体含量逐渐增加,侧板条铁素体和粒状贝氏体组织减少;当热输入较低时粗晶区组织为板条贝氏体,随着热输入的增加,粗晶区组织逐渐由板条贝氏体转变为板条贝氏体+粒状贝氏体,当线能量达到32.2kJ/cm时几乎全部为粒状贝氏体;随着热输入增加,接头抗拉强度逐渐降低,焊缝冲击韧性先提高后降低,但影响有限,热影响区冲击韧性则逐渐降低,当热输入达到32.2 kJ/cm时接头性能恶化,焊接接头在线能量为23.8 kJ/cm时能获得优良的强韧性匹配。     

机器人自动焊焊接接头低温冲击韧性优化研究

在机器人全自动焊接工艺开发过程中，存在其焊接接头低温冲击功不满足焊接标准要求或者离散度较大的现象。为解决此问题，针对多个可能影响机器人自动焊焊接接头低温冲击韧性的因素，制定不同的焊接方案，进行焊接试验及焊后焊接接头低温冲击功测试，并对得到的数据进行离散度分析。经对比发现，不同影响因素对于焊接接头低温冲击韧性影响大小不一，热输入及焊材牌号的影响最大。施工效率最高的焊接方案为：采用M60焊材，以1.0～1.25 kJ/mm的热输入焊接，采用气刨清根并配以打磨，背面填充采用药芯气保焊，配以L71焊材焊接，按照此方案开展实验，结果表明焊接接头的低温冲击功在-40℃时仍满足规范要求。     

焊接热输入对6082铝合金焊接接头组织性能的影响

6082铝合金薄板焊接接头热影响区存在明显的软化现象,拉伸试验时试样的断裂位置多数在热影响区,焊接接头常因抗拉强度不足而导致焊接工艺评定试验失败。通过严格控制焊前工艺准备,采用TIG焊接工艺,研究了不同焊接电流和焊接速度下焊接热输入对6082铝合金焊接接头组织和性能的影响。发现对于厚度为3 mm的6082铝合金试板,焊接热输入控制在0.291～0.334 kJ/mm时,焊接接头的抗拉强度可满足要求。     

电磁焊接过程板件碰撞仿真分析

利用所设计板件焊接试验台对两1 mm厚一系铝板进行了电磁焊接试验,利用扫描电子显微镜（SEM）对样件波状焊接界面的微观形貌进行观察.为解释其形成原因,对电磁焊接过程中两被焊板件的撞击过程进行3D数值模拟,获得该过程中飞板所受垂向应力变化规律及撞击速度变化曲线,仿真结果与试验所观察现象相符.通过分析焊接接头界面和撞击点应力与撞击速度关系,表明撞击应力并非由撞击速度单独决定,还与撞击位置有关,撞击速度、撞击应力及材料的流动性共同导致了波状焊接界面的形成,对其进行合理控制是改善焊接效果的关键.     

HYD36板材的焊接性试验研究

为了分析HYD36钢控轧板和正火板的焊接性,采用埋弧自动焊、气体保护焊进行试验.从试验结果看,HYD36钢在埋弧自动焊热输入为52 kJ/cm的大线能量和气体保护焊热输入为9.9 kJ/cm的小线能量焊接条件下,焊接接头的性能优良,优于国家标准规定的最低值,能满足钢结构件的工艺技术要求.     

Q345超细晶粒钢的焊接性能

对7.5 mm厚Q345超细晶粒钢板卷进行了两种焊丝(φ1.2 mm药芯和实芯)3种热输入(4～10 kJ/em)的系列CO2气体保护焊接试验,研究了焊丝和热输入对焊接接头组织和性能的影响.结果表明,热输入为4 ～ 10 k.J/cm的气体保护焊,可得到满足性能要求的焊接接头;热输入为4～6kJ/cm时,焊接接头粗晶区主要由贝氏体和马氏体构成,且药芯焊丝接头粗晶区马氏体含量高于实芯焊丝接头粗晶区,导致了药芯焊丝接头粗晶区较高的硬度;热输人为10 kJ/cm时,焊接接头粗晶区主要由铁素体构成.拉伸试验和硬度试验表明,母材是焊接接头中的薄弱部位.冲击试验结果表明,焊缝区、热影响区冲击性能与母材在同一水平.     

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。