Deformation Mechanisms of γ′ and γ″ Co-precipitates in IN718

Abstract

Alloy 718 is widely used in gas turbine engines. Even though recent studies have been focusing on the unique deformation mechanisms of the tetragonal γ″ phase as compared to those of the cubic γ′ phase, γ′ and γ″ often co-precipitate and form composite particles. The deformation mechanisms of these composite particles have not been investigated in detail. In this work, we use a combination of ab initio and microscopic phase field methods to study shearing of a dual-lobed type γ″/γ′/γ″ composite particle by various dislocations. Complicated fault structures within both γ′ and γ″ phases are predicted, and some of them have been observed in the experiment. The difficulty associated with experimental characterization of the fault structures in the co-precipitates is also discussed.