Two-phase microstructure-based crystal plasticity constitutive model for nickel-based single crystal superalloys incorporating Re effects on rafting and dislocation evolution

The unique two-phase microstructure of nickel-based single crystal superalloys (NBSCSs) imparts exceptional high-temperature mechanical properties, promoting the use of NBSCSs for turbine blades. A moderate addition of rhenium (Re) can further enhance the mechanical properties by influencing dislocation evolution within the two-phase microstructure and mitigating rafting. The present work aims to quantitatively correlate dislocation evolution and rafting in the two-phase microstructure with the macroscopic mechanical behavior of NBSCSs. To this end, a representative volume element (RVE) consisting of a cubic precipitate surrounded by horizontal and vertical matrix channels is built, and a micromechanical homogenization method based on small perturbation analysis is adopted. To improve the computational efficiency while maintaining a reasonable accuracy, an approximate algorithm is proposed. Based on this, a two-phase microstructure-based crystal plasticity (CP) constitutive model that incorporates Re-influenced dislocation evolution mechanisms and accounts for Re-influenced evolution of the two-phase microstructure (i.e., rafting) has been developed. Using a unified set of constitutive parameters, this CP model successfully predicts both the instantaneous plasticity and prolonged-time creep behaviors of NBSCSs under various temperatures, loading rates and loading orientations. It is noteworthy that the influence of Re doping on both dislocation evolution and rafting is considered in the present CP model, significantly enhancing its ability for describing the mechanical behavior of NBSCSs.