Atomic-scale investigations on dislocation-precipitate interactions influenced by voids in Ni-based superalloys

Abstract

The interaction between dislocations and precipitates plays an essential role in strengthening mechanisms of the Ni-based superalloys (γ-Ni, γ′-Ni3Al). It is worth noting that voids as unavoidable defects in alloys may dramatically affect the mechanical performances of materials. In this paper, the strengthening mechanism of precipitates γ′ and the weakening mechanism of atomic-scale voids are systematically investigated through molecular dynamics (MD) simulations. It is shown that the strength improvement for the Ni-based superalloys mainly benefits from the formation of misfit networks, stair-rod dislocations and Frank dislocations, which reveals atomic-scale details of experimentally observed dislocation-precipitate interaction mechanisms. In addition, considering the void effect, the computational results suggest that the associated Shockley partial dislocations can swimmingly enter into the precipitate γ′ along the periphery of voids and then glide smoothly, which manifests that the resistance of precipitates to the dislocation slip suffers from attenuation so that the mechanical strength reduces.