Effects of Heat Treatment on Microstructure and Low Cycle Fatigue Life of GH4169 Alloy

The GH4169 alloy was treated using three heat treatment processes and the corresponding microstructures and the low cycle fatigue properties at the strain amplitude of 1.0%, 0.8% and 0.5% at room temperature were studied. The results show that the δ phase was precipitated in the microstructure of GH4169 alloy after the three heat treatments. The grain sizes before and after heat treatment had little difference. When adding a 900 ℃ solution treatment between solution and two-step aging treatments, the amount of δ phase precipitation in the alloy increased and more δ phases were obtained with longer holding time. The δ phase amounts almost had no influences on the fatigue lives of the GH4169 alloy. And the fatigue fracture surface at the same strain amplitude exhibited similar morphology. The number of crack sources increased with the increase of strain amplitude.