6. Effect of Heat Treatment on High-Temperature Low-Cycle Fatigue Behavior of Nickel-Based GH4169 Alloy

The effect of heat treatment on the strain-controlled fatigue behavior of Nickel-based GH4169 alloy at 650 °C was investigated. The volume fraction of δ phase increases as the longer solution annealing time. The maximum phase fraction reaches 13.79% after double-aging heat treatment. At the same time the yield strength and the tensile strength of GH4169 alloy decrease gradually. The heat treatment had almost no effect on fatigue life at strain amplitude higher than 0.6%. However, the fatigue life slightly increased with increasing the solution annealing time at strain amplitude lower than 0.5%. The alloy does not exhibit dual-slope Coffin-Manson relationships at 650 °C. The needle-like δ phase obstruct movement of dislocations. This makes the alloy exhibited the high-temperature fatigue life higher than the room-temperature fatigue life at low strain amplitude.