焊接温度对碳钢/奥氏体不锈钢扩散焊接头界面组织及性能的影响

采用真空扩散焊接方法对Q235A低碳钢与AISI304奥氏体不锈钢进行固相扩散连接实验,研究了焊接温度对接头界面组织、力学性能和反应产物的影响。结果表明:Q235A低碳钢/AISI304奥氏体不锈钢复合界面附近形成了合金铁素体层(Ⅱ区)和增C层(Ⅲ区),界面两侧异相组织通过扩散结成共用晶界。在焊接温度850℃,焊接压力10 MPa,焊接时间60 min条件下,接头强度和韧性达到最大值,高于Q235A低碳钢母材。焊接温度过低(≤800℃),接头中析出碳化物Cr_(23)C_6,焊接温度过高(≥900℃),接头中会产生二次碳化物和金属间化合物,脆性的化合物偏析相使接头强韧性显著下降。严格控制焊接温度在850℃区间,并在焊后迅速淬火越过低温区,可有效避免脆性化合物偏析,从而保证扩散焊接头的性能。     

压焊

爆炸焊不锈复合钢板结合面裂纹的判定，超声波焊接振动问题的数值仿真方法，电阻焊时的测量和文件化也很重要，基于稳定分布的铝合金点焊接触电阻，用于预埋件丁宇接头电阻焊的新工艺和成套设备，采用Cu—Sn合金镀层扩散焊焊接Q235钢，用扩散焊进行多层不锈钢打印喷头的实体制造。[编者按]     

大截面钢/铝摩擦焊接头力学性能及显微组织分析

针对大截面铸态纯铝与Q235钢异种金属.采用连续驱动摩擦焊技术进行焊接试验,通过光学显微镜观察、电子探针分析、常温和高温拉伸性能及硬度测试,探讨了其焊接接头的微观组织和力学性能.研究表明,大截面铸态纯铝与Q235钢间具有良好的摩擦焊接性,焊接接头强度等于或高于铝基材;高温条件下,试样均断于铝端母材,抗拉强度随着温度的升高呈现出明显的下降趋势,而伸长率随温度升高而增大;焊接接头在近缝区发生了晶粒细化,在粘塑性层内发生了一定程度的原子扩散,形成扩散层.     

Q235与316L异种钢焊接接头的显微结构与力学性能研究

以Q235低碳钢和316L奥氏体不锈钢为母材,采用手工焊条电弧焊,用A042焊条堆焊,A022焊条填充,对Q235/316L进行焊接.焊后对焊接接头分别进行300、500和700℃保温2h时效处理.处理后对焊接接头进行力学性能测试及断口分析.试验结果表明:经300℃×2h时效处理的焊接接头比经过500℃×2h、700℃×2h时效处理的接头具有更加优异的综合性能.这是由于300℃时效处理的接头组织有利于淬硬相和残余碳化物的溶解,不会出现脆化相,接头组织更加均匀.     

Fe3Al/Q235异种材料扩散焊工艺

探讨了Fe3Al／Q235异种材料扩散焊合适的焊接工艺，利用扫描电镜(SEM)和显微硬度计观察测量了Fe3Al／Q235真空扩散焊接头形态及显微硬度分布，分析了工艺参数对接头性能的影响。结果表明，真空扩散焊加热温度1080℃，加压9．8MPa，保温60min得到的Fe3Al／Q235接头界面结合良好，在扩散界面无明显脆硬相出现，有利于避免接头处出现裂纹，改善Fe3Al／Q235焊接接头的性能。     

喷熔修形后的焊接接头残余应力有限元分析

采用Ni60合金粉末对Q235B钢焊态十字接头进行了氧—乙炔火焰喷熔处理,同时进行了高频疲劳试验.分析认为喷熔修形改善了焊接接头的几何外形.喷熔修形态十字接头在2×106循环周次下的疲劳强度比原始焊态提高了64.5%.基于氧—乙炔火焰喷熔工艺参数,采用ANSYS12.0软件对喷熔过程进行了热-应力耦合的有限元模拟,分析...     

焊接接头的强度

利用低温破断方法对不锈钢焊接接头蠕变断口形貌的分析，Fe3Al与Q235钢异种材料扩散焊的界面剪切强度，薄壁6061铝合金TIG焊接结构强度研究，铝-锂合金焊接接头金属的强度和韧性。[编者按]     

大截面钢/铝异种金属摩擦焊接工艺研究

采用连续驱动摩擦焊技术对大截面铸态纯铝与Q235钢异种金属进行了焊接工艺试验,通过扫描电镜(SEM)分析接头和断口形貌,测试接头力学性能及其电阻率,得到了纯铝与Q235钢焊接接头的力学性能与焊接参数的关系。结果表明,大截面铸态纯铝与Q235钢间具有良好的摩擦焊接性,焊接界面宏观断口呈均匀银灰色,焊接情况良好,具有100%焊合的特征;采用优化焊接工艺参数施焊的焊接接头力学性能可以达到或超过铝侧基材;接头电阻率介于两侧母材电阻率之间。     

Al2O3-TiC/Q235真空扩散钎焊界面组织及抗剪强度

为了获得Al2O3-TiC陶瓷基复合材料与Q235钢的接头,采用Ti/Cu/Ti复合中间层对Al2O3-TiC复合材料与Q235低碳钢进行了真空扩散钎焊。通过扫描电镜、能谱分析和电子探针、抗剪试验等测试方法对Al2O3-TiC/Q235扩散钎焊界面的组织、成分及结合强度进行分析。结果表明,控制加热温度为1110℃,可获得界面抗剪强度122MPa的Al2O3-TiC/Q235扩散钎焊接头,Ti/Cu/Ti复合中间层与Al2O3-TiC和Q235润湿性较好,并发生一定程度的扩散反应,在Al2O3-TiC与Q235之间形成厚度约80μm的界面过渡区,过渡区内形成的组织结构主要是Ti3AlC2,Fe2Ti,Cu和TiC。     

FeCrAl合金真空扩散焊焊接工艺与性能

采用真空扩散焊接方法对FeCrAl合金薄板进行了搭接焊.研究了扩散焊焊接工艺参数对接头质量的影响.在金相显微镜下对接头微观组织进行了观察,采用INSTRON1185万能拉伸试验机对接头试样的拉伸性能进行了测定.试验结果表明,焊接温度、焊接压力和保温时间对接头质量有很大的影响.FeCrAl合金在不填加中间层的情况下即可获...     

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。