Shearing of γ′ precipitates in Ni-base superalloys: a phase field study incorporating the effective γ-surface

Abstract

An extended phase field model of dislocations in Ni-base superalloys is presented. It incorporates the recently developed effective γ-surfaces for both matrix and precipitate phases, obtained from atomistic simulations. These novel γ-surfaces feature extrinsic stacking faults as additional local minima. Thus, they offer an increased number of available dislocation dissociation pathways within the phase field system. The new model has been used to simulate a variety of mechanisms for γ′ precipitate shearing proposed in literature. A critical assessment is made based on the modelling observations.

Keywords:

• primary creep
• dislocation dissociation
• phase field model of dislocations
• Shockley partials
• extrinsic stacking faults

Acknowledgements

The authors would like thank the following people for their invaluable assistance with the theory and discussion: Prof. Gunther Schoeck of Universität Wien, Prof. Yunzhi Wang and Dr. Ning Zhou of the Ohio State University, Dr. Chen Shen of GE Global Research and Prof. Roger Reed of the University of Birmingham. Funding from EPSRC under grant number EP/D047684/1 (Alloys by Design) is also acknowledged with gratitude.