The effects of microstructure and temperature on the deformation heterogeneities and fatigue behavior of a Ni-based superalloy

This research investigates the coupling effect of microstructure and temperature on the fatigue performance of an equiaxed Ni-base superalloy, EA, at design-significant temperatures (750-930 degrees C) for different strain amplitudes (Delta epsilon/2). It is observed that distinguishing damage features (specific to the temperature and Delta epsilon/2) remarkably affect the extent and distribution of strain localization, leading to the divergence in associated fatigue behaviour. The strain is uniformly distributed at lower Delta epsilon/2 for all temperatures. Compared to the 850 and 930 degrees C, the strain localizations at 750 degrees C are more effectively alleviated, accounting for the highest fatigue life. Moreover, this alloy exhibited a bilinear Coffin-Manson (C-M) relationship. It is ascertained that the strain localization resulting from the dislocation and precipitates (gamma ', Cr6C23, and gamma-gamma ' eutectic) interactions are mainly responsible for the dual-slope C-M behaviour.