TC4钛合金电子束焊接头性能研究

采用真空电子束焊方法进行TCA钛合金的焊接，借助OM、SEM设备观察焊缝金属显微组织和断口形貌，测试了焊接接头硬度并进行了冲击试验，分析了焊接接头性能、显微组织及焊缝中气孔的形成。结果表明，采用真空电子束焊焊接TCA钛合金时，焊缝和热影响区金属中较粗大的原始β相一部分转变为过饱和的针状马氏体；焊缝中心有少量的针状α’相，并形成了编织状α组织；焊缝金属的硬度值比母材金属的高，但冲击韧度比母材金属的低。     

7 mm厚TC4钛合金电子束焊接头组织和性能

采用真空电子束焊对7 mm厚TC4钛合金板进行焊接,利用光学显微镜对焊接接头显微组织进行表征,分析不同区域显微组织,通过显微硬度、拉伸试验、冲击试验、弯曲试验对力学性能进行测试,借助扫描电镜对拉伸、冲击断口形貌进行观察,对焊接接头显微组织演变规律和性能进行研究。结果表明,真空电子束焊焊接接头成形良好,TC4钛合金母材组织由α相和β相组成,焊缝区组织由原始的β相转变而成α′相（针状马氏体）,为粗大的柱状晶组织,热影响区组织由均匀且细小的针状马氏体α′相及原始的α相和β相组成;焊缝区显微硬度高于热影响区和母材区,从焊缝顶部到根部显微硬度逐渐下降;焊接接头抗拉强度高于母材抗拉强度;V形缺口在焊缝区的冲击试样具有较好的韧性。     

TC4钛合金电子束焊接接头组织和性能

通过室温拉伸、室温缺口拉伸、显微硬度以及金相分析对TC4钛合金电子束焊接接头的显微组织和性能进行了研究。试验结果表明，用电子束焊接TC4钛合金可获得性能良好的焊接接头，其接头的抗拉强度不低于母材，焊缝的缺口敏感系数均小于1。焊缝区和热影响区的硬度均高于母材，焊缝组织是由较粗大的原始β相转变而成的α′相，即针状马氏体，热影响区组织为均匀且细小的针状马氏体和原始α相的混合物。     

铸造TC4合金电子束焊接工艺研究（英文）

主要探讨铸造TC4合金电子束焊接工艺。为了获得良好的铸造TC4合金电子束焊接接头,作者对焊缝形貌,微观组织和接头拉伸性能进行研究。结果表明:通过调节焊接电流和焊接速度可以获得电子束焊双面成型工艺,但是对于厚板却很难获得双面成形的焊缝形状,经X射线检测焊缝内部质量,能满足检验标准;铸造钛合金电子束焊接接头微观组织构成的母材由板条状α相和β相组成,焊缝区域由针状马氏体组成,热影响区由细针状马氏体、板条状α相和β相组成;铸造TC4电子束焊接接头拉伸性能与母材相当,因此可以通过改善母材的组织成分和显微组织来提高其焊接接头的拉伸强度。冲击试验表明应力集中系数对吸收功有很大的影响。     

Study on the Electron Beam Welding Process of ZTC4 Titanium Alloy

主要探讨铸造TC4合金电子束焊接工艺。为了获得良好的铸造TC4合金电子束焊接接头,作者对焊缝形貌,微观组织和接头拉伸性能进行研究。结果表明:通过调节焊接电流和焊接速度可以获得电子束焊双面成型工艺,但是对于厚板却很难获得双面成形的焊缝形状,经X射线检测焊缝内部质量,能满足检验标准;铸造钛合金电子束焊接接头微观组织构成的母材由板条状α相和β相组成,焊缝区域由针状马氏体组成,热影响区由细针状马氏体、板条状α相和β相组成;铸造TC4电子束焊接接头拉伸性能与母材相当,因此可以通过改善母材的组织成分和显微组织来提高其焊接接头的拉伸强度。冲击试验表明应力集中系数对吸收功有很大的影响。     

TC11钛合金厚板电子束焊接组织及性能

采用大功率电子束对TC11钛合金40mm厚板进行焊接,观察焊缝微观组织并分析其对力学性能的影响。结果表明,电子束焊接接头焊缝形成定向特征的柱状晶,显微组织为针状α′,随着焊缝深度增加,形成的针状α′更细更短。焊缝显微硬度高于热影响区和母材。随着焊缝深度、焊缝硬度增加,而热影响区和母材显微硬度没有明显变化。电子束焊接接头各项力学性能均达到国家军用标准GJB 2744《航空用钛及钛合金自由锻件和模锻件规范》,抗拉强度和屈服强度与母材相当,但是断后伸长率和断面收缩率相比母材略有降低。拉伸试样断口全部位于母材区域,断裂方式为典型的韧性断裂。     

TC4/TA17异种钛合金激光焊接接头显微组织和力学性能

研究TC4/TA17异种钛合金激光焊接接头的显微组织和力学性能。结果表明,TC4/TA17异种钛合金激光焊接头焊缝的显微组织为片状α′马氏体,TC4侧靠近母材的热影响区和TA17侧靠近母材的热影响区只发生α相向β相转变,TC4侧靠近焊缝的显微组织为残余α相+针状α′马氏体,TA17侧靠近焊缝的显微组织为残余α相+片状α′马氏体。TC4/TA17异种钛合金激光焊接头的显微硬度呈不对称分布,焊缝的显微硬度最高,TA17母材显微硬度最低。TC4/TA17异种钛合金激光焊接接头断裂在TA17母材,断口呈现韧性断裂形貌。     

电子束焊接热输入对Ti-6Al-4V组织结构的影响

利用SEM、TEM和显微硬度等方法对TC4的接头焊缝区域进行了分析。结果发现焊接热输入能量的大小与分布模式对焊缝晶粒尺寸有重要影响 ,焊接热输入为 4 8.0kJ/m表面聚焦模式时 ,焊缝组织较为均匀 ,晶粒尺寸为 35 0 μm。随着焊接热输入的逐渐增大 ,焊缝结晶形态由等轴晶向柱状形态演化 ,粗大的针状α +β相和马氏体α′相从单向长针状转换为多向短针状。电子束的热输入模式亦对焊缝金属中的位错分布及形态有较大影响 ,随着热输入的增大 ,焊缝中产生的位错密度逐渐增大 ,但与母材相比仍然较少。焊缝处显微硬度随电子束焊接热输入模式的不同会有明显的变化 ,这可能与焊缝中形成针状α +β相的形态及分布方式有关。焊接热输入为 4 8.0kJ/m表面聚焦模式时显微硬度的分布较为均匀化 (4 0 4 - 4 80HV)。     

厚板TC4钛合金电子束焊接头组织和力学性能研究

对30 mm厚TC4钛合金进行电子束焊接试验,通过金相分析以及显微硬度测试对焊接接头的显微组织和力学性能进行了研究。结果表明,TC4钛合金母材由等轴α以及部分β转变组织组成,焊缝区组织在纵向上具有不均匀性。焊缝顶部β柱状晶粗大,沿熔合线向顶部生长,中部和下部柱状晶相对较小,垂直熔合线向焊缝中心对称竞相生长。β晶粒内部微观组织为针状马氏体,马氏体尺寸从焊缝顶部到底部逐渐减小。热影响区显微组织为等轴初生α相和α'针状马氏体,以及未完全转变的β相。焊缝区和热影响区显微硬度值高于母材;在焊缝区纵向上,顶部显微硬度值为340 HV,随着距离焊缝顶部距离的增加,硬度值显著增大,最大值为435 HV。     

电子束焊接热输入对Ti-6AI-4V组织结构的影响

利用SEM、TEM和显微硬度等方法对TC4的接头焊缝区域进行了分析。结果发现焊接热输入能量的大小与分布模式对焊缝晶粒尺寸有重要影响，焊接热输入为48．0kJ／m表面聚焦模式时，焊缝组织较为均匀，晶粒尺寸为350μm。随着焊接热输入的逐渐增大，焊缝结晶形态由等轴晶向柱状形态演化，粗大的针状α β相和马氏体α‘相从单向长针状转换为多向短针状。电子束的热输入模式亦对焊缝金属中的位错分布及形态有较大影响，随着热输入的增大，焊缝中产生的位错密度逐渐增大，但与母材相比仍然较少。焊缝处显微硬度随电子束焊接热输入模式的不同会有明显的变化，这可能与焊缝中形成针状α β相的形态及分布方式有关。焊接热输入为48．0kJ／m表面聚焦模式时显微硬度的分布较为均匀化(404-480HV)。     

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。