First-principles investigations of the interaction between alloying atom and dislocation and its implication to the rafting of Ni-based superalloys

Abstract

The rafting of the microstructure of Ni-based superalloys significantly deteriorates the mechanical properties. According to the plastic rafting model based on the dislocation mechanism, the directional atomic diffusion induced by the interaction between the alloying atom and the interfacial dislocation is critical to the evolution of the rafting microstructure. In the present work, the interactions between the alloying atom and dislocation core in both matrix γ phase and the precipitate γ′ phase are investigated by using a first principles method in combination with the semi-discrete variational Peierls-Nabarro dislocation model. We show that the alloying atoms Al, Cr, Co, Mo, Ru, Ta, W, Re lower the (edge for Cr and Co) dislocation core energy in the γ phase, indicating that the alloying atoms are attractive to the dislocation core. For the γ′ phase, Cr, Mo, Ta, W, Re raise whereas Co and Ru lower the dislocation core energy, i.e., Cr, Mo, Ta, W, Re are repulsive but Co and Ru are attractive to the dislocation core. With the calculated interaction between the alloying atoms and the dislocation core, the influence of these alloying elements on the rafting of the superalloy is discussed.

Keywords

• Ni-based superalloys
• First-principles
• Generalized stacking fault energy
• Dislocations
• Rafting