The effects of microstructure and temperature on the deformation heterogeneities and fatigue behaviour 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°C) for different strain amplitudes (Δϵ/2). It is observed that distinguishing damage features (specific to the temperature and Δϵ/2) remarkably affect the extent and distribution of strain localisation, leading to the divergence in associated fatigue behaviour. The strain is uniformly distributed at lower Δϵ/2 for all temperatures. Compared to the 850 and 930°C, the strain localisations at 750°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 localisation resulting from the dislocation and precipitates (γ′, Cr6C23, and γ-γ′ eutectic) interactions are mainly responsible for the dual-slope C–M behaviour.