钛合金薄壁筒形件热旋成形技术研究

采用TA15钛合金开展钛合金薄壁筒形件热旋成形技术研究,针对钛合金热旋过程中出现的典型缺陷进行形成机理和控制方法研究,成功地旋制出了质量良好的BT20钛合金大型薄壁筒形件.研究表明,钛合金薄壁筒形件热旋成形的关键是保证金属旋压时变形流动的均匀性,其直接受到热旋加热方式、旋压工艺参数和成形模具等因素的影响.BT20钛合金合适的旋压温度范围为600～700℃,当坯料较厚时温度可稍高以防止裂纹,而坯料较薄时旋压温度可适当降低以防止坯料隆起;钛合金筒形件壁厚越薄,越容易产生鼓包和褶皱等成形缺陷,尤其是当厚径比(t/D)小于1%时,应采用较小的道次减薄率以防止局部失稳;采用较小的工作角和较大的旋轮圆角半径有利于促进旋压变形的均匀性.     

TC4钛合金锥形件温热剪旋实验研究

薄壁钛合金锥形件广泛应用于航空航天及军事工业部门,现有的加工方法已无法满足高精度零件的要求,火焰加热温热强旋成为大型钛合金锥形件成形的重要加工方法.本文对TC4钛合金锥形件温热剪旋工艺进行了实验研究,给出TC4钛合金不同工艺条件下的成形情况,分析了缺陷产生的原因.确定了可行的TC4钛合金锥形件温热剪旋工艺,为采用温热剪旋工艺进行钛合金锥形件的批量生产奠定基础.     

退火温度对TC2钛合金织构与冲压性能的影响

研究了不同退火温度下TC2钛合金的显微组织、晶粒取向、拉伸性能和冲压性能。结果表明,TC2钛合金在退火过程中,晶粒的取向从横向(TD)方向偏向法向(ND)方向分布;随着退火温度从600℃升高到800℃,TC2钛合金的拉伸应变硬化指数降低,塑性应变比升高,冲压成形性能有所提高;当退火温度控制在700~800℃范围内时,TC2钛合金具有较好的冲压成形性能。     

TC4钛合金筒形件的热旋成形工艺研究

轻质、高强、耐热、耐蚀钛合金零部件在航空航天、兵器等发动机领域中具有重要的应用前景。针对一端带内法兰的TC4钛合金筒形件开展了加热旋压成形工艺研究,分析了加热温度、旋轮形状、旋压道次、旋轮进给比、壁厚减薄率等工艺参数对TC4钛合金旋压成形的影响规律,研究了旋压过程中材料出现的破裂、起皱、扭曲、扩径等现象并提出了解决措施,辅以后续精密整形和热处理工艺,制造了几何尺寸和机械性能均满足要求的TC4钛合金筒形件,为类似钛合金筒形件旋压成形提供了参考。     

耐热粉末铝合金筒体热旋成形试验

介绍了喷射沉积耐热铝合金管坯经挤压变形,变薄旋压筒体的研制过程;重点论述了热旋成形筒体的工艺路线。试验探讨了耐热铝合金的旋压温度为350－450℃,道次变薄率约为20％,累计变薄率约50％,需中间退火,退火温度宜取350℃。热旋结果认为,喷射沉积耐热粉末铝合金铸坯直接热旋成形困难,需经挤压比大于4的变形致密,有助于热旋成形。耐热粉末铝合金挤压坯加热变薄旋压,应采用小压下量多道次的变形过程,逐渐细化晶粒组织,才能旋出综合性能良好的筒形件。     

钛合金筒形件强力旋压工艺模拟

采用ANSYS软件对不同工艺参数下钛合金TC4筒形件的强力旋压过程进行了模拟,获得了成形角、减薄率、进给率等工艺参数对等效应力和旋压力的影响规律,为TC4旋压工艺参数的选择和优化提供了依据。     

大长径比薄壁铝合金壳体成形工艺研究

利用数控旋压机研究了长径比1.59的5A06薄壁铝合金贮箱壳体的成形工艺,并用金相显微镜、力学拉伸试验分析了旋压和退火处理对旋压件显微组织和力学性能的影响.结果表明:对于此种大长径比薄壁铝合金贮箱壳体,采用热旋压预成形+车加工半球面+终成形旋压的工艺是可行的;通过控制合理的旋压加热温度、进给比、间隙等参数,研制的壳体壁厚、内径完全满足图纸要求;与原始板材相比,退火热处理后的终成形旋压件晶粒细小,在保持良好塑性的同时,屈服强度提高20MPa以上.     

薄壁封头电磁感应加热旋压工艺

火箭燃料贮箱薄壁球面封头,由于其具有大径厚比、弱刚性的特点,利用传统旋压加工方法容易出现封头结构失稳现象。提出薄壁封头电磁感应加热旋压成形的工艺方法,采用MSC.Marc有限元软件建立了薄壁封头加热旋压三维有限元仿真模型。研究了主要工艺参数——旋压温度T、进给率f和旋轮圆角半径r对封头壁厚均匀性的影响,以及温度场对法兰稳定性的作用。结果表明:在合理范围内,提高旋压温度、增大旋轮圆角半径和减小进给率可以提高成形件质量。最终确定优化工艺参数为:r=4 mm,f=1.35 mm·r-1,T=250~300℃。通过开展封头电磁感应加热旋压实验,验证了电磁感应加热旋压工艺方案能有效抑制法兰起皱并提高工件壁厚均匀性。     

TC4钛合金管材的强力旋压

TC4合金管材的制造是一个难题，其变形抗力大、加工硬化显著、易开裂．对于厚壁TC4管材，可以用锻造、挤压、钻孔的方法生产；对于薄壁TC4音材，一般使用轧制和旋压的方法生产．采用轧制方法生产时，需对坯料进行加热，温度在400℃～500℃，要有专门的温轧机头，因而造成加工设备复杂、工艺复杂、生产成本高．采用旋压方法生产，从查到的文献着都是热旋，旋压温度在800℃一900℃，冷旋则少见成功的报道．美国制管公司80年代初的文章指出，TC4合金冷旋是可行的，变形量可以达亚％，但同时又宣布国许多因素未搞清楚，不具备工业生产的条件…     

TC4钛合金f450 mm棒材不同厚度整体试样热处理工艺研究

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　　通过对TC4钛合金f450 mm棒材80、40、20 mm整体试样热处理工艺的研究,分析不同的热处理温度和热处理冷却方式对棒材横、纵向组织和室温、高温力学性能的影响。结果表明：当整体试样厚度不大于40 mm,且采用双重退火（首次退火后水冷）的热处理工艺时,才能保证TC4钛合金f450 mm棒材的室温力学性能和显微组织符合GJB 1538,高温强度≥615 MPa。双重退火制度为：首次退火工艺为加热到b转变温度以下30～80℃,保温不少于1 h,水冷;随后再进行700～800℃,保温1～4 h,空冷。     

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。