铝合金焊接工艺与接头组织相关性的研究

利用光纤激光器与TIG交直流电焊机实现了6 mm厚2014高强铝合金的激光热传导焊、激光深熔焊和激光-TIG电弧复合焊,并借助于激光共聚焦扫描显微镜对其接头形貌特征和接头微观组织进行了分析。结果表明,焊接接头的熔深、熔宽、熔合线宽度、软化区宽度、焊缝中心区晶粒尺寸与焊接工艺具有显著的相关性,三种焊接工艺下得到的软化区和焊缝中心区等轴晶晶粒尺寸远小于目前采用的填丝TIG焊焊接工艺。     

激光深熔TIG复合焊电弧特性及熔池行为的研究

对10 mm的Q345B板进行光纤激光与深熔TIG旁轴复合焊接实验,探究激光与电弧的最佳复合方式,利用高速摄像系统观测电弧形态和熔池行为的变化,并分析激光对电弧和熔池的影响机制。实验结果表明:焊枪垂直,激光倾斜30°的复合方式所得到的焊缝熔深最大。复合焊接利用激光增强熔池金属流动的特性弥补了深熔TIG高速焊接焊缝无法成型的缺陷。     

低碳钢激光预熔活性焊接法

以8 mm厚的低碳钢为研究对象,在氧气的保护下,用小功率光纤激光在待焊焊件表面进行预熔处理,使表面熔化生成一层氧化层,然后用TIG焊或激光电弧复合焊覆盖氧化层,研究工艺参数对焊缝成形的影响.结果表明,激光预熔后进行覆盖焊接,电弧没有收缩,熔深增加到1.5倍左右,表面成形良好.随着电流的增加,熔深增加,但激光预熔后的焊道增加更快.随着焊接速度的增加,熔深减小.随着激光预熔功率的增加,熔深增加.随着复合焊接中激光功率的增加,熔深增加.焊缝含氧量的增加,使得表面张力温度系数由负变正,是低碳钢激光预熔活性焊接熔深增加的主要原因.     

光纤激光辅助TIG焊焊缝成形特点及影响因素分析

在活性焊接法研究的基础上提出了激光辅助TIG焊方法.焊前在氧气保护下采用小功率激光器熔化焊道表面,然后用常规TIG焊覆盖激光预熔焊道,从而可使熔深增加,熔宽减小.结果表明,激光预熔和未预熔焊道熔深、熔宽均随焊接电流的增加而增加,但激光预熔焊道熔深增加的更快;焊接速度的增加使激光预熔和未预熔焊道熔深、熔宽均减小;随激光功率增加,焊道熔深增加,熔宽减小;随预熔速度的增加,熔深先增大后减小,熔宽先减小后增大.综合最佳参数后可以得到焊缝熔深增加明显、焊缝表面成形良好的焊道,从而可以发展为一种新的活性焊接法.     

不锈钢光纤连续活性激光焊的研究

光纤激光器与活性焊接技术相结合可大幅增加焊缝熔深,提高焊接效率。以TiO2、SiO2、Cr2O3、CaF2和NaF五种活性剂为基础,通过均匀配方设计,获得了15组不同成分的复合活性剂配方,针对SUS304不锈钢板进行光纤连续活性激光焊,研究了氟化物和氧化物对熔深和熔宽的影响,从而获得了最佳配方。试验结果表明:在复合活性剂作用下,焊缝的熔深均有明显的增加,当含氟化物较多时,熔深最大达到1.0 mm,深宽比最大可达1.5,与未涂敷活性剂相比,提高了73%。焊缝的显微组织为粗大的柱状晶,中心存在少量等轴晶,焊缝底部存在明显偏析。     

建筑装饰用AA5754铝合金在激光电弧复合焊接过程中焊缝形貌及性能变化

激光复合焊接是将激光热源和附属焊接源进行组合焊接的技术。利用新一代高功率光纤激光器和TIG焊枪,采用激光电弧复合焊接技术完成了两套实验。研究激光功率、焊接速度和电弧电流对建筑装饰用AA5754铝合金焊接质量的影响,并对以电弧为主导作用的复合热源和以激光为主导作用的复合热源进行比较分析。结果表明:以激光为主导作用的复合焊有更好的熔深和焊接质量,并在实际工作中得到了进一步验证。     

工艺参数对304不锈钢脉冲Nd∶YAG激光/TIG电弧复合焊焊缝成形的影响

研究了304不锈钢脉冲Nd:YAG激光TIG电弧复合热源焊接工艺参数对焊缝成形的影响.结果表明,脉冲Nd:YAG激光/TIG电弧复合焊焊缝横截面面积大于单一激光焊焊缝横截面面积与单一TIG焊焊缝横截面面积之和,具有协同效应;激光功率增大时,复合焊焊缝熔深和熔宽均增大,复合焊焊缝横截面面积增大,复合热源热效率也增大;离焦...     

铝合金激光-小功率脉冲MIG电弧复合热源焊接特性分析

针对5A06铝合金,通过一系列对比数据综合分析了MIG焊和激光MIG复合热源焊接技术在焊缝熔深、焊缝成形、焊接速度、焊接热输入等方面的优缺点.结果表明,在MIG平均电流小于200 A的小功率脉冲MIG电弧区域内,等热输入且等焊接速度条件下,激光-MIG复合热源焊接技术与MIG相比可以提高焊缝深宽比1～2倍,增加焊缝熔深0.43～2.5倍;等热输入且等平均焊接电流条件下,与MIG相比,激光MIG复合热源焊接技术可以提高焊接速度0.6～1.5倍,增加焊缝熔深0.5～5.9倍;激光MIG复合热源焊接技术可以用高于MIG焊0.6～6.5倍的焊接速度和更小的焊接热输入获得与MIG同样的焊缝熔深;与MIG焊相比,激光MIG复合热源焊缝的铺展性更好,更适合于高速焊接;MIG复合2 kW的激光能量后会增加平均电弧电压、减小平均电流.     

激光-TIG复合热源焊接钛合金T形结构焊缝成形特点及影响因素分析

采用激光-TIG弧复合焊接工艺对钛合金T形结构单面焊背面双侧一次成形焊接新技术进行了研究,通过综合试验、对比分析等方法,研究了多种试验条件下T形结构焊缝成形特点及影响因素,给出了采用激光-TIG复合焊接工艺实现钛合金T形结构单面焊背面双侧一次成形焊接的最佳工艺方案.结果表明,采用激光-TIG复合焊接工艺焊接钛合金T形结构与钨极氩弧熔透焊工艺相比在焊缝组织、焊接效率、焊缝成形、间隙适应性等方面有明显的优势.     

一种新的活性焊接方法

提出一种新的活性焊接方法,首先使用激光在氧气保护下熔化焊件表面,使焊缝表面的氧含量增加,然后使用普通的TIG焊覆盖激光焊缝,以此达到增加熔深的目的.我们称此焊接方法为激光辅助活性TIG焊接法.在同一焊接规范下,激光辅助活性TIG焊比普通TIG焊熔深明显增加,熔宽减小.     

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.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

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).     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

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.