超塑性在合金加工和焊接方面的应用

超塑性在航空航天等行业零件加工中应用越来越广,各国研究人员对其均有很大兴趣。本文对超塑性的发展情况给予介绍,综述超塑性在合金加工和焊接方面的原理和特点,并举出超塑性成形中的超塑等温锻造、气压成形、超塑挤压成形方法,以及国内外应用实例和超塑在焊接中的应用及国内外应用实例。     

全国钛合金成形技术暨第六届超塑性学术研讨会在上海召开

由北京航空制造工程研究所主办 ,中国航空第一集团公司科技发展部、中国锻压学会超塑性专业委员会及中国航空学会工艺专业分会协办的全国钛合金成形技术暨第六届超塑性学术研讨会于 2 0 0 2年 1 2月 9日～ 1 2日在上海召开。来自于海军、空军、航空、航天、兵器部门和大学、研究院所以及材料生产等 50多个单位的近 1 2 0名代表出席了会议。会议就钛合金成形技术研究、材料超塑性理论及实验研究、钛合金 SPF/ DB结构的设计技术、钛合金的焊接和表面处理、新型材料的开发以及钛合金管材加工技术等专题进行了广泛的交流 ,宣读论文近 30篇。充…     

镁合金的应用及其塑性成形技术

文章介绍了镁及镁合金的特点,总结了镁合金在汽车、自行车、航空航天、3c产品、武器等方面的应用,阐述了镁合金塑性加工技术的现状,提出了塑性成形是镁合金产品成形的发展方向.     

液压成形技术及其在汽车工业中的应用介绍

液压成形技术由于其出色的零件成形质量、相对简单的加工工艺,被广泛应用于汽车、航天航空等制造业。主要介绍了管材和板材液压成形的技术原理和特点、国内发展现状以及在汽车工业中的应用,同时也简要介绍了超高强钢液压成形技术在汽车零件制造方面的应用。液压成形技术虽具有一定优势,但在汽车板材成形和超高强钢零件的工业化生产方面还有待发展。     

基于DEFORM的金属压力加工数值模拟

介绍了塑性成形有限元分析软件DEFORM的模块结构,并通过实例分析介绍了该软件在网格划分、应力和应变分析、载荷计算、点的跟踪和温度耦合分析等方面的应用。     

新型PMS塑料模具钢超塑性成形及强化

利用ＰＭＳ镜面塑料模具钢进行恒温超塑性试验，利用试验参数对话机键模进行超塑性精密成形，并对其组织结构、宏观强度及其强化机制进行了研究分析。指出，由于超塑性变形导致ＰＭＳ钢的位错强化、沉淀强化和细晶强化，使其在超塑性精密成形的同时能有效地提高强度。     

钛及钛合金板材拉深成形的影响因素与技术进步

钛及钛合金相对铝、钢等金属材料塑性差、极限变形量小、成形时回弹大,拉深成形相对困难。介绍了钛及钛合金拉深成形的影响因素及其对成形的影响,综述了钛及钛合金拉深成形在各向异性控制、压边力控制、计算机模拟以及加热方法等方面的技术进步,指出了未来研究人员应充分利用计算机模拟技术,对影响钛及钛合金冲压成形的各种因素及其之间的相互关联建立详尽的数据库,以便该成形工艺在钛及钛合金零部件的成形得到更广泛的应用。     

TC1深型腔负角度零件超塑成形模具设计与优化

钛合金在航空、航天等工业中有广泛的应用,其中TC1钛合金在变形温度为860℃,应变速率为7.5×10-4 s-1时,延伸率最大可达710%,具有良好的超塑性,通过超塑性气压成形工艺可成形形状较为复杂的零件。根据深型腔负角度钛合金法兰盘零件的特点,提出了超塑性气压成形工艺,并根据零件尺寸特征设计了弧形底面和平底两种的模具,同时,根据TC1拉伸力学特性建立了材料的高温本构关系,应用MARC有限元对其超塑成形过程进行了模拟。结果表明,弧形底面模具成形零件最薄处为1.2 mm,壁厚分布标准差为0.198 mm,变薄率为40%,在成形过程中最大应力约6.6 MPa;而平底模具成形的零件最薄处仅为0.82 mm,壁厚分布标准差为0.303 mm,变薄率高达59%,在成形过程中最大应力约7.8 MPa。因此弧形底面模具厚度分布较均匀,壁厚减薄较小,最大应力较小,降低了应力集中程度,是该类零件超塑成形工艺较为理想的模具。     

航空航天用钛合金盘件开发与应用

钛及钛合金具有比强度高、耐腐蚀、耐高温等优良性能,在航空航天、舰艇、化工等领域得到日益广泛的应用.阐述了航空航天用钛合金盘件的研究现状,重点介绍了高性能钛合金盘件的制备工艺,包括粉末冶金热等静压成形和超塑性等温锻造成形.分析了钛合金盘件在航空航天领域的应用现状,并探讨了航天航空用钛合金盘件的发展趋势.     

高性能钛合金先进成形技术研究现状

主要介绍先进热成形技术、脉冲电流辅助成形技术和电磁辅助成形技术的特点,及其在钛合金薄壁板材成形中应用的研究进展.热成形是钛合金塑性加工应用最为普遍的成形工艺,利用高温下钛合金塑性变形软化的特征,能够实现复杂钛合金零件的成形.脉冲电流和电磁辅助成形技术目前尚未开展大规模的产业应用,其在高强度难成形材料的成形加工方面具有潜在应用前景.     

Experimental Studies on the Superplastic Forming of Square Shaped Components and Diffusion Bonding Characteristics of Ti–6Al–4V Alloy

Superplasticity is the ability of a polycrystalline material to exhibit, in a relatively isotropic manner, large elongations when deformed in tension. This property is exploited during superplastic forming in the fabrication of complex-shaped components which are otherwise technically difficult or economically costly to form by conventional methods. The ability of some titanium alloys to undergo superplastic deformation coupled with their diffusion bonding capability provides excellent opportunities to fabricate intricate parts resulting in significant cost and weight savings, particularly in the manufacture of aerospace structures. In the present work, experimental studies on the superplastic forming of square shaped components from titanium alloy Ti–6Al–4V sheets of 2 mm thickness that are commonly used in aerospace structural applications are reported. Superplastic forming of suitably sized blanks was carried out at temperatures of 1,148 K (875 °C), 1,173 K (900 °C) and 1,200 K (927 °C) using constant argon gas pressures of 1, 1.4 and 1.8 MPa. The formed components were characterized for their thickness distribution, mechanical and metallurgical properties. Diffusion bonding characteristics of the alloy sheet of 1 mm thickness were investigated for varying time durations at different temperatures and 4 MPa stress under an argon atmosphere and lap shear strength values of the joints are reported. Efforts were then made to carry out diffusion bonding concurrent with superplastic forming (SPF/DB). For these experiments, two sheets of 1 mm thickness each were superplastically formed into square components of size 80 mm square and 60 mm deep with an initial forming cycle followed by a diffusion bonding cycle by subjecting the component to a static pressure (higher than the forming pressure) for a specified period of time, which ensured good bonding between the two sheets. The components formed by the SPF/DB process were compared with those formed from the monolithic 2 mm sheet and the results are presented.     

TC4钛合金工艺进展

文章总结了近年来针对TC4钛合金的成分开发,并进一步围绕TC4钛合金论述了增材制造、超塑成形、粉末冶金、精密铸造等近净成型技术的研究进展。     

Experimental studies on the superplastic forming of square shaped components from sheets of Ti-6Al-4V alloy

Superplasticity is the ability of a polycrystalline material to exhibit, in a relatively isotropic manner, large elongations when deformed in tension. This property is exploited during superplastic forming in the fabrication of complex shaped components which are otherwise technically difficult or economically costly to form by conventional methods. The ability of some titanium alloys to undergo superplastic deformation coupled with their diffusion bonding capability (SPF/DB) provides excellent opportunities to fabricate intricate parts in a single operation resulting in significant cost and weight savings, particularly in the manufacture of aerospace structures. In the present work, experimental studies to characterize the superplastic behaviour of an as-received titanium Ti-6Al-4V alloy sheet commonly used in aerospace structural applications are reported. Tensile test coupons prepared from the alloy sheet were subjected to high temperature tensile tests in the temperature range of 1123 K (850°C) to 1223 K (950°C) and strain rate range of 10^?4 s^?1 to 10^?2 s^?1 in order to characterize the superplastic deformation behaviour. Suitable dies, for superplastic forming of 80 mm × 80 mm square components to depths of 43 and 50 mm, were designed and fabricated. Components were superplastically formed at a temperature of 1200 K (927°C) and 0.7 MPa constant argon pressure. The components were characterized for their thickness distribution, mechanical and metallurgical properties and the results are presented.     

Mechanical properties and microstructures of Al-Mg-Sc alloys

The mechanical properties of Al-(Mg)-0.5Sc alloys have been investigated. Room-temperature tensile and toughness properties were found to reflect a superposition of the properties of Al-Mg and Al-0.5Sc alloys and are quite competitive with high-performance Al alloys. A combination of substructure refinement by Mg and stabilization by Al₃Sc precipitates produces exceptional superplasticity as exemplified by superplastic forming (SPF) elongations in excess of 1000 pct at a strain rate of 0.01 s^-1. Overall, these alloys demonstrate an extremely attractive combination of strength, toughness, density, and SPF fabricability.     

An investigation of superplasticity in a thermomechanically processed U-6nb (α + γ2) alloy

A uranium-6 niobium alloy was shown to exhibit superplasticity. A thermomechanical processing (TMP) sequence was used to develop the ultrafine grain size essential for superplastic behavior. Strain-rate sensitivity, maximum elongation, and flow curve data indicated that this alloy is superplastic above the monotectoid temperature (647 °C) in the equilibrium γ₁, single-phase, temperature regime. The existence of superplasticity in the single-phase temperature regime was explained by the presence of metastable γ₂ at these higher temperatures. Sluggish niobium diffusion and the resultant slow dissolution kinetics were shown to be responsible for this anomalous “single-phase” superplastic behavior. An engineering elongation of 658 pct was obtained at 685 °C for a constant true strain rate of 2.5 × 10^-4 s^-1 which required an initial flow stress of only 2.8 MPa. A grain growth kinetic study, along with flow curve information, has also shown that superplastic forming (SPF) must be completed within 2 hours at 670 °C to obtain maximum ductility with the lowest forming pressure.     

Influence of intense plastic straining on grain refinement,precipitation, and mechanical properties of Al-Cu-Li-Based alloys

Grain refinement is one of the major interests when an ultrahigh strength/ductility combination is demanded for ambient and cryogenic temperature applications, especially when superplastic forming (SPF) is involved for the manufacturing of different aerospace structures. Equal-channel angular extrusion (ECAE) is a relatively new metalworking process, which is capable of producing an ultrafine, submicron-grained (SMG) structure by means of intense plastic straining without a change in the shape or dimensions of the worked material. In the current research work, the influence of ECAE processing on the room-temperature mechanical properties of Al-Cu-Li-Mg-Ag-Zr alloys in the T4 and T6 temper conditions is investigated. An ultrafine SMG structure of 0.2 to 0.4 μm was produced for the ECAE-processed alloys from an initial grain size of >100 μm, which is compared with a conventionally processed superplastic Weldalite sheet material with an ∼1.5 μm grain size. The ECAE processing eliminates the precipitation-free zones (PFZs) in the T6 temper condition without the need for prior stretching. A significant improvement in the mechanical properties at room temperature is achieved by ECAE processing in comparison with conventional processing.     

TC4钛合金负角度零件超塑成形及性能研究

在前期材料实验的基础上对TC4钛合金负角度零件超塑成形过程进行仿真,获得压力-时间曲线和壁厚分布,并根据仿真结果中接触摩擦力分布情况,预测了模具磨损。对仿真获得的压力-时间曲线进行修正,并将修正后曲线作为实际加载曲线进行超塑成形实验,获得负角度零件。比较了零件型腔底端壁厚的实际结果与仿真结果,同时,研究了成形零件的负角度壁壁厚分布、显微组织、力学性能。结果表明:取件温度为300℃时,零件外形及表面质量较好;实际零件型腔底端壁厚分布与仿真结果趋势相同,两者最大误差为4.4%;零件最小壁厚在负角度过渡圆角处,其值为0.66 mm,最大减薄率为67%;负角度壁壁厚标准差为0.186 mm,说明此部位壁厚分布比较均匀;成形后材料的晶粒尺寸长大明显,而室温屈服强度、抗拉强度、延伸率从原始材料的951,1045 MPa,13.9%下降至853,955 MPa,10.8%,说明经过超塑成形后,材料由于晶粒长大而导致力学性能下降。     

Effects of alloy modification and thermomechanical processing on recrystallization of Al-Mg-Mn alloys

The 5083 Al alloy (Al-4.75Mg-0.8Mn) holds potential for superplastic forming (SPF), but slow rates of forming limit its use for many applications. Higher strain rates are believed possible through the development of finer grained microstructures or stabilized subgrain structures. Grain sizes after recrystallization and recrystallization characteristics are known to be dependent on the amount and distribution of second-phase particles in the matrix. In this study, the concentration and sizes of such particles were varied by additions of particle-forming elements of Mn and Zr and by modifications of the rolling and aging schedules (thermomechanical processing (TMP)). The investigation involved studying recrystallization kinetics at different temperatures and correlating the grain sizes with particle sizes and volume fractions. The addition of Mn and Zr, for the composition ranges and TMP methods studied, resulted in a substantial reduction of the recrystallization kinetics, but complete suppression of static recrystallization (or subgrain stabilization) was not observed. However, statically recrystallized grain sizes as small as 6 μm were achieved.     

BTi -62421S高温钛合金超塑成形与焊接工艺研究

设计了新型高温钛合金BTi - 62421S舵面模拟件超塑成形模具,结合超塑成形与几种典型焊接技术,研究了激光焊、滚焊等焊接方法对超塑成形的影响,最终研制出钛合金舵面模拟件超塑成形零件.结果表明采用激光焊与滚焊工艺都能很好地保证两层钛合金板气密性要求,激光焊接工艺效率更高、表面质量更好,选择适当的激光焊接工艺参数可获得...     

Development of forming limits for superplastic formed fine grain 7475 AI

Forming limits in conventional sheet metal forming are given by strain levels obtainable prior to the onset of a localized neck or tear in the sheet. While the external appearance of such a neck is not observed in superplastic metals until strains become quite large, the formation of internal cavities could dictate the tolerable levels of strain in formed components. In this paper, these useful strain limits for a superplastic 7475 Al alloy have been explored. The approach used was to establish the influence of strain state (uniaxial, plane strain, and balanced biaxial) on the inception and growth characteristics of cavities and to correlate the extent of cavitation with material properties. Based on these data, it was then possible to establish strain states for which little or no loss in properties was observed, and thereby to define forming limits for superplastic forming this material. These results, coupled with comparisons against strains developed in actual parts as well as analytically predicted strains, show that a wide range of structural parts can be superplastically formed within the constraints of the recommended forming limits.