发动机用TiAl涡轮与转轴摩擦焊接过程中，在焊合区会产生脆性过渡相，从而影响接头性能。为揭示TiAl基合金与GH3039合金摩擦-扩散双重焊焊合区过渡相的形成规律，探究过渡相的晶体结构和断裂性能，采用在焊接过程中中断焊接的方法，取得了双重焊不同阶段的接头。采用SEM研究了这些接头焊合区过渡相的形貌及其演变规律；利用TEM及配套的原位纳米力学测试系统，研究了过渡相的晶体结构及Al-Ni-Ti三元金属间化合物相的裂纹扩展行为。结果表明，在摩擦焊及其热处理过程中，焊接界面上陆续发生相变形核并初步长大形成新的过渡相：Ni₃(Al, Ti)、(Ni, Cr)_SS、Al₃NiTi₂、AlNi₂Ti和Ti₃Al。随后的扩散焊接过程中的压力和高温促进Ti₃Al和Al₃NiTi₂形成稳定的双相区，促使(Ni, Cr)_SS区调幅分解形成相互交错呈柱状分布的fcc结构(Ni)_SS和bcc结构(Cr)_SS。Al₃NiTi₂和AlNi₂Ti相内弥散分布着极少的α相纯Ti，α-Ti与Al₃NiTi₂相界处于非共格状态。Al₃NiTi₂和AlNi₂Ti分别具有六方和bcc结构。在原位压缩过程中，Al₃NiTi₂相内裂纹的形核和扩展，均没有发现明显的塑性变形和位错运动。但观察到裂纹尖端附近晶格面发生微区变形，原子排列从有序结构转变为无序结构。

During the friction welding process of TiAl turbine and shaft used in engines, brittle intermediate phases will be generated in the welding zone, which affects the joint performance. To reveal the formation rules of the intermediate phases in the friction-diffusion double welding zone between TiAl-based alloy and GH3039 alloy, and investigate the crystal structure and fracture properties of the intermediate phases, the joints at different stages of the double welding were obtained by interrupting welding during the welding process, respectively. The morphology and evolution law of the intermediate phases of these joints in the welding zones were analyzed using SEM; the crystal structures of the intermediate phases and the crack growth behaviors of Al-Ni-Ti ternary intermetallic compound phases were analyzed using TEM and an in situ nanomechanical testing system.Results showed that during friction welding and heat treatment, phase transformation and nucleation occurred on the welding interface and preliminarily grew up to form the following new intermediate phases: Ni₃(Al, Ti), (Ni, Cr)_SS, Al₃NiTi₂, AlNi₂Ti, and Ti₃Al. In the subsequent diffusion welding process, the pressure and high temperature promoted the formation of a stable two-phase zone between Ti₃Al and Al₃NiTi₂. The amplitude-modulated decomposition in the (Ni, Cr)_SS zone formed fcc (Ni)_SS and bcc (Cr)_SS that are staggered and distributed in a column. Dispersions of pure Ti with the α phase could hardly be found in the Al₃NiTi₂ and AlNi₂Ti phases, and the phase boundary between α-Ti and Al₃NiTi₂ was in an incoherent state. Furthermore, Al₃NiTi₂ and AlNi₂Ti exhibited hexagonal and bcc structures, respectively. During the in situ compression process, neither obvious plastic deformation nor dislocation movement was observed in the nucleation and propagation of cracks in the Al₃NiTi₂ phase. However, the lattice surface near the crack tip underwent microdeformation, and the ordered structure of atomic arrangements became disordered.