A microstructure-based model was developed to simulate the mechanical behaviour of polycrystalline Ni-based superalloys containing gamma’ and gamma’’ precipitates and processed by casting and forging.

The model was based on a multiscale approach in which deformation and failure mechanisms as well as microstructural features and defectology are progressively incorporated at three different levels: micron-sized single crystals and small size polycrystals, polycrystalline specimens and components. In this way, the microstructural features which control the mechanical performance (precipitate structure, grain size, texture, porosity, surface condition, etc.) can be taken into account at the appropriate length scale.

The basic tool to predict the mechanical performance of polycrystalline specimens were the finite element simulation of a representative volume element of the microstructure. Crystal plasticity models for Ni-based superalloys were used to simulate the grain behaviour and the model parameters (as well as the grain boundary properties) were obtained from micromechanical tests on single crystals and bicrystals milled from the polycrystalline specimens by focus ion beam in both cast and forged materials. As opposed to purely phenomenological models, relevant microstructural parameters (grain size, texture, etc.), process-specific defects (shrinkage porosity, inclusions, light etching features, etc.), and surface condition can be accounted for in this strategy by modifying the geometric features of the representative volume element.

The proposed model was able to address the effect of temperature (from room temperature up to 700ºC) in the mechanical properties used in the design of components: tensile strength, fatigue, crack propagation and creep. In addition, statistical aspects associated with the scale up from polycrystalline specimens to actual components were incorporated.