Insight into element segregation mechanisms during creep in γʹ-strengthened Co-based superalloy by elastoplastic phase-field simulation

Abstract

The element segregation accompanying the creep process has been shown to significantly affect the deformation resistance of the superalloys. However, the processing and mechanism of element segregation are still unclear. This paper investigated the concentration evolution of a model Co–9Al–9W (at. %) alloy during 900 ​°C/275 ​MPa using developed ternary elastoplastic phase-field model coupled with CALPHAD method and crystal plasticity model. The results of simulation show that co-depletion of Al and W element occurs in γʹ precipitate and in γ side at γ/γʹ interface, and this depletion is gradually increasing with the accumulation of plastic strain. From the perspective of changes of driving force of element diffusion, it is found that these segregation phenomena are attributed to the high elastic potential caused by the large local plastic strain. In addition, the effects of these segregations on creep property are also predicted. The current research provides a new method for exploring the mechanism of element diffusion.