针对GH4169合金的Delta工艺, 通过950 ℃高温拉伸实验研究了δ相对GH4169合金的高温拉伸变形行为的影响. 结果表明: 初始δ相含量为8.21%的GH4169合金的拉伸应力-应变曲线为典型的弹性-均匀塑性型; 且在均匀塑性变形阶段表现为2个不同的变形阶段, 其中第1阶段的加工硬化指数n为0.494, 大于第2阶段的加工硬化指数0.101; 其拉伸断裂机制为延性断裂的微孔聚集型断裂机制, 其中δ相和碳化物是变形断裂中微孔形成的核心, 因此δ相的存在使得合金的高温塑性降低, 在GH4169合金的Delta工艺中必须控制δ相的析出含量.

GH4169 alloy is an important material used for aviation and aerospace engines because of its excellent mechanical properties in the temperature range from -253 ℃ to 650 ℃. In order to improve the safety and reliability of engines, it is crucial to obtain the forging with a uniform and fine microstructure. Generally, theforgings with large size and complex shape, such as turbine disks and engine shafts, are manufactured by multi-stage hot working processes. In addition, the microstructure of the alloy is sensitive to the hot deformation parameters. Therefore, the defects of coarse grain and duplex grain always appear in the forgings. As the δ phase in the alloy can control grain growth through the strong pinning effect, the Delta process (DP) has been developed, which uses an intentional δ phase precipitation cycle and subsequent thermomechanical processing to produce uniform fine grain billet and bar stock. In this work, for the DP of GH4169 alloy, the effect of δ phase on the tensile deformation behavior of GH4169 alloy at high temperature was studied by the tensile tests at 950 ℃. The result indicated that the tensile stress-strain curve of the GH4169 alloy with 8.21% pre-precipitated δ phase was the elastic-uniform plastic curve, and there were two different deformation processes during the uniform plastic deformation stage. The strain hardening exponent in the first deformation process was 0.494, which was higher than 0.101 in the second  process. The fracture mechanism for the pre-precipitated δ phase alloy was microvoid coalescence ductile fracture, and the δ phase and carbide were the nucleuses for the formation of micropores. Thus, the existence of the δ phase made the high-temperature plasticity of GH4169 alloy decrease, and the content of the pre-precipitated δ phase must be controlled in the DP of GH4169 alloy.