Finite-Element Crystal Plasticity on Phase-Field Microstructures: Predicting Mechanical Response Variations in Ni-Based Single-Crystal Superalloys

The mechanical response of Ni-based single-crystal superalloys is known to be sensitive to the microstructural state, i.e., the shape and size of the γ′ precipitates when exposed to high-temperature conditions. The magnitude and sign of the natural lattice misfit between the γ and γ′ phases play the most crucial role in establishing a controlled size, shape, and distribution of γ′ precipitates during heat treatments as well as in defining the direction of rafting, viz. the directional coalescence of the γ′ precipitates. In this study, a bottom-up scale bridging strategy of using phase-field informed finite-element (FE) crystal plasticity on realistic microstructures is followed to better understand the effect of the microstructural state on the macro-scale performance of a 001\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \left\langle {001} \right\rangle $$\end{document}-oriented Ni-based single-crystal superalloy. Strain-controlled tensile tests using FE crystal plasticity were performed on a set of different microstructural states: cuboidal, rafted, and topologically inverted imported from 3D phase-field simulations. The study revealed that a cuboidal microstructure with a natural lattice misfit of − 0.004 is the most ductile. As observed experimentally, the microstructure with rafts perpendicular to the loading axis (N-type) is more ductile than the cuboidal one. The P-type microstructure, i.e., with rafts parallel to the loading axis, is found to have the lowest ductility, which was attributed to lesser dislocation mobility.