Stacking fault in γ′ precipitate of single crystal nickel base superalloy DD8 after out-of-phase thermomechanical fatigue

The microstructures of single crystal nickel base superalloy DD8 were investigated after out-of-phase(OP) thermomechanical fatigue(TMF). It is found that gamma' precipitates are sheared by Schockley partial dislocations, which is different from the case in which gamma' precipitates are sheared by (1/2) [110] dislocation pair under isothermal fatigue (IF). It is presumed that whether gamma' precipitates are sheared by Schockley partial dislocation or by dislocation pair is related to both deformation rate and stress amplitudes at the appropriate temperature.