晶粒尺寸对GH720Li镍基合金蠕变-疲劳寿命的影响

The creep-fatigue experiments were conducted in nickel-based superalloy GH720Li, one of the most important turbine disk materials, at an elevated temperature of 650°C with different grain sizes, to investigate the influence mechanism of grain size on the creep-fatigue life of GH720Li. Results show that the creep-fatigue life of GH720Li superalloy decreases with the decrease of grain size. SEM fracture analysis indicates that the oxidation and cracking are the main mechanism of GH720Li in the process of creep-fatigue at high temperature, and the smaller grain size will result in the longer length of grain boundary. Finally, two methods including the damage function based on hysteresis energy and the applied mechanical work density (AMWD) are modified to predict the creep-fatigue life of GH720Li, which match well with experimental data.