Thermo-mechanical deformation evolution in polycrystalline Ni-based superalloys by a hierarchical crystal plasticity model

Abstract

A hierarchical plasticity constitutive model is employed to comprehend the fundamental relations between microstructural morphology, crystal orientations, deformation mechanisms and the mechanical response over a wide range of operating temperatures for polycrystalline nickel-based superalloys. A parametrically homogenised, crystal plasticity constitutive law accounting for the variation in the subgrain-scale morphology allows for efficient modelling at the polycrystalline scale with information from the lower scales. This framework incorporates the effects of non-Schmid mechanisms, anti-phase boundary shearing and geometric features of the substructure. A major outcome of this study is the observation that at elevated temperatures, a slip mode transition occurs from the octahedral slip systems to cube slip systems that induces a reversal of many critical mechanical properties. The polycrystalline microstructure is significantly weakened, and plastic deformation completely shifts to grains for which the orientation corresponds to the greatest resolved shear stress on cube slip systems.