Effect Of δ Phase On Low Cycle Fatigue Behavior Of Ni-based Superalloy GH4169

Ni-based superalloy has been widely used in critical hot components of aero engine because of its high temperature strength, oxidation resistance and resistance to fatigue and creep properties. But the application technology of superalloy developed by our country in aero engine is not very mature, and one of the reasons is lacking of systematic understanding to the relationships between microstructure and consisted phases of domestic superalloys with their performance. Based on the above issues, the domestic turbine disk material GH4169 alloy was prepared by using different heat treatments in this paper and mainly investigated the effect of 8 phase on the tensile and low cycle fatigue behavior of this alloy. The main contents and conclusions could be summarized as follows:(1) The GH4169 alloy was prepared using three different heat treatments and the microstructures of the alloy were greatly influenced by heat treatment parameters. After heat treatment, different amounts of δ phase precipitated in the microstructures of the alloy.(2) The study of room temperature tensile tests showed that the tensile behavior of GH4169 alloy could be significantly affected by δ phase. With the increase of amount of 8 phase, the strength of the alloy decreased and the ductility increased. And there were some differences in the tensile fracture morphologies due to the amount of δ phase.(3) The low cycle fatigue life of GH4169 alloy at room temperature could hardly be affected by 8 phase. The alloy with different amount of 8 phase exhibited similar fatigue lie. The plastic line in the Coffin-Manson relationship of the alloy had a dual slope characteristic. Meanwhile, the cyclic deformation behavior, fracture mode and deformation mechanism were corresponding analyzed in this paper.(4) The low cycle fatigue life of GH4169 alloy under 650℃ at high strain amplitudes (△εt/2≥0.6%) could hardly be affected by 8 phase. At low strain amplitude (△εt/2=0.5%), the fatigue life had a certain dispersion and increased with the increase of content of 8 phase. The plastic line in the Coffin-Manson relationship didn’t have the dual slope characteristic.