Finite-Element Crystal Plasticity on Phase-Field Microstructures: Predicting Mechanical Response Variations in Ni-Based Single-Crystal Superalloys
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2019, The Minerals, Metals & Materials Society. 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 precipitates when exposed to high-temperature conditions. The magnitude and sign of the natural lattice misfit between the and phases play the most crucial role in establishing a controlled size, shape, and distribution of precipitates during heat treatments as well as in defining the direction of rafting, viz. the directional coalescence of the 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 -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.
