Ti2AlNb双层结构脉冲电流辅助超塑成形/扩散连接控形控性控构基础研究

With the development of the new generation of aerospace vehicle, the demand for the complex structure of the light and high temperature endurable materials is increasing. The heating cycle of traditional superplastic forming process is long, the heating capacity is limited. It is difficult to meet the need of forming Ti2AlNb alloys and the new type of high temperature resistant materials. Based on the deep research of the recent years, this project put forward pulse current assisted superplastic forming/diffusion bonding method to fabricate the hollow structure with Ti2AlNb sheets. Using pulse current effect of high density in the metal materials to produce Joule heat and electro-plasticity effect, the instant heating and high temperature diffusion bonding of Ti2AlNb plate will be realized. So that material flow stress is decreased and the plasticity is increased. Using inert gas pressure to achieve rapid forming and diffusion bonding, the hurt of the long time high temperature on the microstructure and properties will be decreased, high temperature oxidation damage will be reduced too. The low cost and high efficiency forming of Ti2AlNb based alloy hollow multilayered complex components could be realized. Through the combining research on the experimental study on the process, performance test, microstructure analysis, mechanical properties characterization and numerical simulation, the mechanical behavior and deformation mechanism of the Ti2AlNb during the heat deformation, diffusion welding mechanism.of the interface, high temperature deformation coordination mechanism between the weld and the parent material, under the pulse current effect of high density, could be explored. This will provide the theoretical basis for integrated control the microstructures and properties of the complex structure of Ti2AlNb base alloy.

随着航空航天飞行器的发展，轻质耐高温材料的需求日益增加。传统的超塑成形方法难以满足Ti2AlNb基合金等新型耐高温材料的成形需要。本项目在近几年深入研究的基础上，提出Ti2AlNb基合金空心结构脉冲电流加热超塑成形/扩散连接成形方法，利用脉冲电流作用于材料时，将产生焦耳热和电致塑性，实现Ti2AlNb板材瞬间加热和高温扩散连接，使材料流动应力降低，塑性增加；利用惰性气体加压实现快速成形和扩散连接，降低长时间高温加热对材料组织和性能的损伤，减少高温氧化，实现低成本高效率的Ti2AlNb基合金空心多层复杂构件成形。通过工艺实验研究、性能测试、组织分析、力学性能表征、数值模拟相结合，探究高密度脉冲电流作用下，Ti2AlNb基合金板材高温热变形中的力学行为与变形机制、界面扩散焊接机制、焊缝与母材高温协调变形机制，为Ti2AlNb基合金复杂结构的组织性能一体化控制提供理论基础.

节能和轻量化现已成为全球汽车产业和航空航天领域的发展趋势和各国竞相追逐的工业目标。轻质材料和绿色节能技术成为我国学者和工程师研究的重点方向及热点领域。诸多轻质的高性能材料不断地涌现，其中以Ti2AlNb合金为代表的金属间化合物被认为是一种可以取代镍基高温合金的潜在高温合金材料。与此对应的环境友好型的材料加工技术被研发和应用于商业生产中，其中电流辅助热加工工艺凭借其灵活的技术相容性和快速加热优势，已经与多种传统工艺结合（如冲压、轧制、增量成形、气压胀形、搅拌摩擦焊和压力焊）。为进一步克服传统超塑成形和扩散连接工艺的固有劣势，拓宽Ti2AlNb合金的应用领域，本文提出了电流辅助超塑成形/扩散连接工艺，该工艺可以应用于大尺度的合金板材，应用的电流强度和抽真空时长降低；研究了Ti2AlNb合金板材的静态加热行为；采用电流辅助超塑气胀（EASPF）工艺和炉温气胀工艺成形了Ti2AlNb合金自由胀形件；系统地研究了Ti2AlNb合金板材的电流加热的宏微观行为、电流辅助超塑气胀工艺和电流辅助扩散连接工艺。最后采用电流辅助SPF/DB工艺成功试制了Ti2AlNb合金双层结构。