Plasticity-induced stacking fault behaviors of γ′ precipitates in novel CoNi-based superalloys

Implementation of novel gamma/gamma' Co-based superalloys with higher strength and improved creep durability is a challenging task for researchers. The lack of atomic-level understanding of plastic deformation behavior has seriously limited the exploration of the full capacity of Co-based alloys. We put forward a comprehensive study of generalized stacking fault energies by first principles to explore the effect of Ni and Al/W on the plastic deformation mechanism of gamma' precipitates in Co-based superalloys. It is found that alloying Ni and adjusting Al/W obviously change the dislocation glide and twinning nucleation in the gamma' precipitates by altering the stable fault energies and the unstable fault energy barriers. Excessive addition of either Ni or W deteriorates the strength even the stability of alloys. The ratio of effective planar fault energy (Delta E-p) bridges intrinsic energy barriers and various deformation mechanisms of superalloys at elevated temperatures. Except for alloying effects, the grain orientation also significantly governs the operation of the plastic deformation of superalloys. Our theoretical results agree with the available measurements and well capture the observed phenomena in experiments. (C) 2021 Published by Elsevier Ltd on behalf of Chinese Society for Metals.

Automated summary

This study investigates the effects of Ni and Al/W on the plastic deformation mechanism of gamma' precipitates in Co-based superalloys using first principles. The results show that alloying Ni and adjusting Al/W significantly alter dislocation glide and twinning nucleation, with excessive addition of Ni or W deteriorating strength. The ratio of effective planar fault energy plays a crucial role in bridging energy barriers and deformation mechanisms in superalloys at elevated temperatures.