钛铝合金作为一种新型轻质高温结构材料，具有优异的高温强度、抗氧化性和抗蠕变性能，被认为是替代镍基高温合金的首选材料。 作为高温结构件，在服役过程中承受高温与循环载荷的共同作用，因此需要对其在高温下的疲劳行为进行研究。 超声疲劳试验作为一种疲劳测试高效率手段，可大大降低细致分析合金疲劳失效机制的时间成本。基于此，结合超声疲劳试验设备与中高频感应加热装置，探究了 650 ℃下 Ti-48Al-2Cr-2Nb 合金的循环变形行为。 结果表明，在 650 ℃下 Ti-48Al-2Cr-2Nb 合金不存在疲劳极限；断裂形式为准解理断裂和沿晶断裂的混合断裂，裂纹在解理的 γ 晶粒附近萌生，并沿晶界扩展，在片层团附近为沿层和穿层的混合断裂模式；随着循环应力幅值的减小，合金的失效方式由短裂纹扩展后形成的长裂纹相互连接所导致的断裂转变为短裂纹间相互连接形成长裂纹所导致的断裂，疲劳寿命分散度减小，断口粗糙度降低。

As novel lightweight high-temperature structural materials, titanium aluminide alloys exhibit excellent high-temperature strength, oxidation resistance, and creep resistance. It is considered the preferred material to replace nickel-based superalloys. As an elevated-temperature structural component, it is subjected to both elevated temperatures and cyclic loads during service, necessitating research into its fatigue behavior at elevated temperatures. Ultrasonic fatigue testing, an efficient means of fatigue testing, can greatly reduce the time cost of detailed analysis of alloy fatigue failure mechanisms. Accordingly, by combining ultrasonic fatigue testing equipment and a medium high-frequency induction heating device, the cyclic deformation behavior of the Ti-48Al-2Cr-2Nb alloy at 650 ℃ was investigated. The results show that there is no fatigue limit for Ti-48Al-2Cr-2Nb at 650 ℃.The fracture mode is a mixture of quasicleavage fracture and intergranular fracture, where cracks initiate near the cleaved γ grains and propagate along grain boundaries. Near the lamellar groups, the fracture mode is a mixture of trans- and interlamellar fractures. As the amplitude of the cyclic stress decreases, the failure mode transitions from fracture caused by long crack linkages following short crack propagation to fracture resulting from the interconnection of short cracks forming long cracks, leading to a reduction in fatigue life dispersion and a decrease in fracture surface roughness.