TA1超薄板激光焊接组织与性能的研究

选用0.5 mm工业纯钛TA1作为研究对象,在不同激光功率下采用不同焊接速度对其进行焊接试验,焊后分析了不同焊接速度对TA1焊缝宏观形貌、显微组织、接头力学性能及硬度、接头耐蚀性的影响。结果表明：随着焊接速度增加,焊缝宽度逐渐减小,焊缝表面成形质量提高;焊缝组织中粗大块状α相逐渐减小,针状α相逐渐增多,晶粒细化;接头抗拉强度逐渐增大并趋于母材强度,耐腐蚀性也越来越好。随着焊接功率增加,焊缝宽度逐渐增加,焊缝组织中粗大块状α相逐渐增加,抗拉强度逐渐降低,耐腐蚀性越差。     

钛及钛合金的焊接

工业纯钛及α钛合金的焊接组织在常温下是单相,根据冷却速度的不同,生成锯齿状或针状组织。各种机械性能与基材相比没有大的变化,焊接性能良好。α β钛合金在从β相冷却的过程中,形成马氏体(α'相),α'相的数量和性质按合金组成和冷却速度而变化。一般情况下,随α'相的增加,合金的延性、韧性降低。即使是焊接性良好的Ti-6Al-4V,当β稳定元素含量大于3%或含钒5%以上时,焊接性能下降。β钛合金的马氏体生成温度低于室温,焊缝处是亚稳β相,所以焊接性不怎么劣化。但因合金元素添加量多,往往缺乏延性。另外,时效和冷加工使合金…     

工业纯钛TA2电镀槽大型裂纹的焊接

通过对工业纯钛TA2电镀槽焊缝大型裂纹产生的原因和纯钛的性能及焊接特点的分析，提出了消除纯钛焊缝大型裂纹，保证焊接质量的工艺措施，并成功地应用于工业纯钛TA2电镀槽的焊接。     

石化装置用工业纯钛的焊接

工业纯钛是一种极为优良的耐腐蚀材料，在石油化工设备上得到广泛应用，由于钛的活泼性和对加热敏感性，因此钛设备的制造，焊接是关键工艺，特别是大型衬钛设备的制造，焊接工作量很大，如何保证质量是生产钛设备的主要问题。本文结合衬钛设备的结构，主要对工业纯钛手工钨极氲弧焊的保护效果，焊接规范参数的选择进行了试验分析，初步掌握了工业纯钛的焊接工艺，并对焊缝的气孔、焊缝金相组织和焊缝污染程度对质量的影响进行了讨论。     

TA2工业纯钛焊接性分析与工艺试验

烟台氯碱项目某腐蚀性装置决定采用TA2工业纯钛材料,在使用前,需对TA2工业纯钛的焊接性做一个全面的分析探讨,本次工艺试验采用了准57 mm×4 mm的TA2工业纯钛管进行GTAW单面焊双面成形的焊接工艺,并分析探讨了TA2工业纯钛特殊的焊接性,制订了详细的焊接操作流程。通过对焊前准备和焊接操作的严格控制,避免了焊接接头中缺陷的产生,通过对焊缝进行探伤及力学性能试验验证,得到了良好力学性能和焊缝组织的焊接接头,并成功应用于实际生产中。     

嵌入纯钛薄板对TA15钛合金电子束焊焊缝成分及显微组织的影响

在TA15钛合金电子束焊对接接头中嵌入纯钛TA1金属薄片,通过改变焊缝的熔宽调控焊缝内的母材与嵌入材料的比例,以此实现对焊缝内合金成分含量的控制。通过对焊接接头及焊缝内元素分布特征的观察和分析,证明选用适当的焊接工艺参数可以实现合金元素的均匀分布,并可有效地细化焊缝组织、降低焊缝的显微硬度。     

TC4/Ta-W合金异种金属电子束焊接

对TC4/Ta-W合金电子束焊接进行了研究,采用偏向钽钨合金一侧进行焊接的方式进行分析.电子束焊接接头成形良好,在一定偏束量时焊缝中Ta和W元素含量较高,焊缝组织为以β钛为基的固溶体组织,无脆性化合物生成,存在富钽区和贫钽区.焊缝中元素分布不均匀,在偏束量为0.6 mm时焊缝中含钛相对较多,约为60%,而钽钨母材熔化相...     

纯钛焊件焊缝组织细化的热加工工艺研究

为解决焊接的纯钛阴极辊生产电解铜箔时在焊缝处出现的周期性色差问题,进行了纯钛焊缝及其表面堆焊部位显微组织细化的热加工工艺研究.结果表明,变形温度太低时,由于焊缝与基体晶粒度级别相差太大,不能协调变形,容易导致交界开裂;温度太高时,又不能有效细化焊接凝同组织;弯折次数不宜太多,否则容易落入再结晶晶粒长大的第二个峰值变形区.     

工业纯钛的焊接

结合衬钛设备的结构,着重对工业纯钛氩弧焊的保护效果,焊接规范参数的选取进行了试验分析,并对焊缝的气孔,焊缝的金相组织和焊缝的污染程度对质量的影响进行了一般性的讨论。     

Ti2AlNb基合金TIG焊接头组织与性能分析

采用不加丝和加丝脉冲TIG焊接工艺焊接了厚度为1.5 mm的Ti2AlNb基合金。观察了焊接接头区的组织形貌,测试与分析了接头的硬度和拉伸性能。试验结果表明,焊缝区为树枝晶组织形貌,而且组织分布出现了分层现象;加纯钛焊丝可以使焊缝的等轴晶区扩大;从母材向热影响区和焊缝区过渡,O相含量逐渐减少;由于相组成的变化,焊接接头的硬度分布规律为热影响区的硬度最高,母材次之,焊缝区最低;不加丝和加纯钛焊丝的焊接接头抗拉强度基本相当,而加纯钛焊丝的焊接接头断后伸长率显著提高;不加丝焊接接头的断裂模式为韧脆混合断裂特征,加纯钛焊丝焊接接头为韧性断裂特征。     

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。