TiAl合金与金属材料的摩擦-扩散复合焊接方法及机理研究

As a new lightweight high-temperature structural materials TiAl Alloy has a strong prospect in high temperature turbine blade manufacturing. But because of its relatively high melting point, low solubility in common metal materials, similar to a brittle phase, so the poor weldability with metal. This project aims at TiAl turbine 42CrMo axis friction welding technology research based on friction - diffusion hybrid welding, friction welding of high temperature, high pressure, short-term, local, large deformation characteristics, realization of TiAl Initial connection to the metal, then using diffusion welding characteristics of high temperature, low pressure, long, through diffusion, recrystallization, interfaces tissue stability and to further improve the connection performance. Using modern analytical methods and first-principles on weld interface of different materials microstructure, structure and fracture morphology of observation, analysis of fracture mechanism, revealing different materials joining mechanism of friction welding interface, determine the organizational structure of the welding interface. According to the variation of organization and performance of TiAl with metal welded joint in long-term work condition of high temperature, the service life of TiAl alloy welded structure will be assessed. Promoting the development of theory of pressure welding of dissimilar materials, promote TiAl alloy in the wider field of application.

TiAl合金作为新型轻质高温结构材料在高温涡轮和叶片制造方面具有强烈的应用前景。但由于其相对于常用金属材料熔点高、溶解度低，类似于脆性相，因此其与金属材料之间的焊接性很差。本项目拟在TiAl涡轮与42CrMo转轴摩擦焊接预先研究基础上，采取摩擦-扩散复合焊接的方式，利用摩擦焊接高温、高压、局部、大变形、短时特点，实现TiAl与金属材料的初步连接，然后利用扩散焊高温、低压、长时间的特点，通过扩散、再结晶，使得界面组织稳定，以提高接头性能。采用现代分析手段及第一性原理对不同材料焊接界面的微观组织、结构和断口形貌进行观察与分析，分析接头断裂机制，揭示性能差异很大的异种材料摩擦焊接界面的连接机理，确定焊接界面的组织结构。根据TiAl 与金属焊接接头在高温长期工作条件下组织和性能的变化规律，评估TiAl 合金焊接结构件的使用寿命。促进异种材料压力焊接理论发展，推动TiAl合金在更广泛领域内的应用。

以坦克发动机TiAl增压涡轮与调质钢轴的连接为应用背景，探讨TiAl/Ni基高温合金异种材料焊接性。针对强规范摩擦焊接过程中TiAl涡轮损伤的关键技术问题，提出并研究了摩擦-扩散复合焊接新方法。通过实际复合焊接，对接头组织进行扫描、EBSD、透射等分析，对接头性能进行宏观力学性能试验和纳米压痕、微米压痕、原位拉伸和断裂韧性试验，揭示了TiAl合金涡轮在压力作用下，裂纹形核和扩展过程中裂纹扩展距离和方向；测得TiAl合金与GH3039摩擦焊接过程中准稳定摩擦阶段界面温度为960~1030 °C，处于TiAl超塑性温度范围；摩擦焊和复合焊的焊合区具有相同的复杂组织结构：TiAl/Ti3Al+Al3NiTi2/Al3NiTi2/AlNi2Ti/Ni3(Al,Ti)+ (Ni,Cr)ss/(Ni,Cr)ss/GH3039，但复合焊焊合区各相更加稳定，各相层更宽，靠近母材的两个双相区内相的分布趋向于柱状有序分布；上述五种中间相中的Al3NiTi2和AlNi2Ti相，硬度最高，但断裂韧性最差；预摩擦焊接接头在后续扩散焊接时，使得Al3NiTi2和AlNi2Ti的断裂韧性得到了较大的提升，将TiAl与GH3039接头的抗拉强度由预摩擦焊接头的236MPa提高至复合焊接头的314MPa；分析了Al3NiTi2和AlNi2Ti相晶体结构。TiAl-42CrMo涡轮轴在高温热处理过程中，接头性能会随着时间和温度的升高而降低。还初步探索了Ti2AlNb与TiAl及42CrMo的摩擦焊接可行性。所提出的摩擦-扩散复合焊接方法丰富了异种材料连接方法，所提出的微区断裂韧性分析方法可以应用在异种材料焊接区中间相的性能分析中。发表论文7篇，其中SCI收录3篇，EI收录2篇；申请专利2项，授权发明专利1项。