Microstructure characterization and damage coupled constitutive modeling of nickel-based single-crystal alloy with different orientations

The mechanical properties of nickel-based single-crystal superalloys are sensitive to temperature and orientation. The present work focuses on the stress and strain responses of a second-generation nickel-based superalloy at different temperatures and with different orientations. Microstructure and dislocation arrangements are observed by scanning and transmission electron microscopy of samples after tensile testing. The results reveal the tensile fracture failure modes and dislocation morphologies (braids, cells, stacking faults, etc.) for different temperatures and orientations. Although the [001] sample shows higher yield strength than the other two orientations, the strain hardening was more significant at [111] orientation and stress softening at [011] orientation due to their different dislocation mechanisms. In addition, a new hardening model and damage evolution law are proposed and coupled with a crystal plastic constitutive model. Numerical analysis results show that the proposed constitutive model can accurately fit the full stress-strain response from tensile experiments for different temperatures and orientations.