Multi-scale crystal plasticity finite element model approach to modeling nickel-based superalloys

Abstract

This paper develops a homogenized, activation energy-based crystal plasticity (AE-CP) model for single-crystal Ni-based superalloys that can be implemented in simulations of polycrystalline aggregates. A size-dependent, dislocation-density-based finite element model of the subgrain scale representative volume element with explicit depiction of the γ–γ′ morphology is developed as a building block for homogenization. Consistent with observations made in the temperature range 650°C⩽θ⩽800°C, mechanisms of subgrain-scale anti-phase boundary shearing and grain-scale microtwinning are included in the model. The homogenized AE-CP model develops functional forms of constitutive parameters in terms of characteristics of the subgrain γ–γ′ microstructural morphology. Specifically, the thermal shear resistance, reference plastic shear strain rate and saturation shear resistance are expressed as functions of γ′ shape, volume fraction and γ channel width in the subgrain microstructure. This homogenized model has the advantage of significantly expediting crystal plasticity finite element simulations due to parameterized representation of the morphology, while retaining accuracy with respect to the explicit representation. A microtwin nucleation and evolution model is introduced in the grain-scale crystal plasticity framework for predicting tension–compression asymmetry. The model is validated with results of single-crystal tension and compression tests available in the literature.