Shear-band-independent segregation-induced strain softening of single-crystal Ni-based superalloys

In the present study, we found that the yield strength of the nickel-based single-crystal superalloys increases with increasing temperatures. However, when the tensile temperature is elevated up to 900 °C, the alloy shows a strain softening behavior without catastrophic shear banding or macroscopic strain localization. The microscopic analysis reveals numerous stacking faults (SFs) generated in the γ′ phase, which is suggested to be facilitated by Co and Cr diffusion. Such strain softening behavior is attributed to the significantly reduced SF energy, but the macroscopic strain localization is resisted by the highly confined evolution of SFs within the γ′ phase.