TC4钛合金的多轴高周疲劳损伤及强度退化研究

不同工况下TC4(Ti-6Al-4V)钛合金疲劳累积损伤及强度退化存在较大差别。为了充分表征载荷参数的影响,基于Chaboche损伤模型以及改进的多轴疲劳损伤准则,提出新的强度退化模型,开展了TC4钛合金的多轴高周疲劳(HCF)寿命预测和强度退化评估。首先,开展TC4合金在一系列加载路径下的多轴比例和非比例疲劳试验。将Chaboche非线性损伤准则和临界平面法与提出的损伤控制参数相结合,描述了TC4合金的非线性疲劳损伤计算和寿命预测。其次,进一步建立了基于累积损伤的非线性强度退化模型,并证明了该模型在不同载荷工况下均可以获得更高的精度。实验结果表明,由于考虑载荷参数的影响,提出的TC4钛合金疲劳寿命与强度退化预测结果精度远高于其他的预测模型。     

基于等效等时应力应变曲线的燃气涡轮叶片多工况蠕变计算

基于等时应力应变曲线理论,提出了一种可用于计算多工况的等效等时应力应变曲线蠕变计算方法。运用该方法计算了某航空发动机燃气涡轮工作叶片,在先后经历4个状态(共150 h)持久试车工作状态后的残余变形,并将变形结果与其他蠕变计算方法以及真实发动机叶片经过150 h持久试车后的计量结果进行了对比分析。分析结果表明,与其他蠕变方法相比,本文作者提出的基于等效等时应力应变曲线蠕变计算方法在保持计算精度的同时,进一步提高了计算效率,更具有工程实用价值。     

等离子喷镀制造纤维增强钛基复合材料

连续纤维增强的钛复合材料是航空发动机压气机部件很有吸引力的材料，然而，它们的制造仍然是材料科学和工程的一个复杂课题．钛基复合材料（TMC）的应用使航空发动机压气机的设计从惯用的盘和燕尾叶片改为TMC叶状环．这种叶状环设计利用复合材料的纵向强度来传输高的圆周应力，并保持足够的横向强度来传输经向应力．制作的示范叶状环部件，预计减重达到70％；还用T14C制造了诸如致动器和压杆．所有TMC制造方法都要求连续的S江纤维和钛合金基体以正确的纤维取向和体积分数精心排列，以获得最佳的力学性能．在制备未加工的TMC预型坯过…     

论TC9高温钛合金在我国航空发动机上的应用

本文论述了TC9合金在某型航空发动机上应用的技术依据,并介绍了我国首次应用TC9合金作该发动机的压气机盘和叶片的情况。     

压气机叶片优化设计软件研发

结合用户需求和发展趋势,设计了一种全新的航空发动机压气机叶片优化设计软件;基于数模参数化生成的方法,实现了航空发动机压气机叶片叶型造型参数化,软件以遗传算法为基础,对航空发动机压气机叶片进行了优化设计性能仿真;性能仿真结果以图、表等多种方式直观表达,结果保存于数据库,增强了数据安全性,完整性;可视化界面及支撑数据库,提高了软件的易用性和人机交互性。经过各方验证仿真优化设计结果稳定准确,表明所研发软件高效可用。     

航空发动机高压压气机叶片损伤检查

压气机叶片是航空发动机中的重要零件,在高温、高压、振动以及巨大的离心力等恶劣的工作环境下,易产生腐蚀、疲劳裂纹甚至断裂等故障。如果不能及时发现这些损伤,会造成发动机空中停车,危及飞行安全。介绍了超声波检查HPC 4级叶片榫头的方法,是一种能有效杜绝安全隐患的方法。     

TC6钛合金锤上自由锻件心部清晰晶形成原因及解决方法

TC6合金是一种综合性能良好的马氏体型(α+β)两相钛合金,其名义成分为Ti-6Al-2.5Mo-1.5Cr-0.5Fe-0.3Si。该合金的使用状态一般为退火状态,也可进行适当的强化热处理。TC6合金具有较高的室温强度,比TC4合金高85MPa,而且在450℃以下具有良好的热强性。TC6合金还具有较好的热加工工艺性能,塑性较高但变形抗力较大,主要用于制造航空发动机或船用燃气轮机低压或高压压气机叶片、接头及紧固件。     

中温高强TC11和TC19钛合金锻件组织与性能研究

针对航空发动机压气机整体叶盘等部件所使用的TC11、TC192种中温高强钛合金锻件，基于其各自典型使用状态，开展了组织形貌和不同条件下拉伸性能、冲击韧度以及保载/无保载条件下低周疲劳性能的对比分析研究。结果表明：TC11钛合金锻件呈现典型的双态组织，TC19钛合金锻件呈现全片层网篮组织；TC19钛合金锻件在100～400℃下的拉伸强度明显优于TC11钛合金锻件。TC19钛合金锻件的高温缺口冲击韧度值明显高于TC11钛合金锻件，在100℃和855 MPa峰值应力载荷下，TC19钛合金锻件的保载和无保载疲劳寿命均明显高于TC11钛合金锻件，且2种合金均存在一定的保载效应。     

TC2钛合金等温锻造双冠叶片低倍组织亮线的原因分析

<正>TC2是一种具有中等强度和较好塑性的近α型高温钛合金材料,主要应用于高性能航空发动机的叶片。TC2含有4%α稳定元素Al和1.5%β稳定元素Mn,名义化学成分为Ti-4Al-1.5Mn。这种合金不能进行热处理强化,只能在退火状态下使用。TC2具有较好的工艺塑性、焊接性和热稳定性,长期工作温度可达350℃,短时使用温度为750℃,在航空工业、宇航工业、化工工业、造船业等方面日益得到广泛的应用。     

青岛滨海学院钛合金高温防护涂层研究取得进展

正钛合金因其具有质轻、高强及高温力学性能优异特性,是高推重比先进航空发动机压气机叶片首选材料。然而,钛合金抗高温氧化和热腐蚀性差,高温氧化环境下,必将造成钛合金压气机叶片因严重高温氧化和热腐蚀失效,降低发动机效率,造成严重事故。戴景杰团队在钛合金表面设计了系列高温防护涂层,并对涂层在800 ℃下1 000 h的循环高温氧化行为和800 ℃下300 h的热腐蚀行为进行了研究,构建了涂层在高温氧化和热腐蚀行为下的损伤模型,阐明了涂层在高温-     

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。