Microstructure-Based Modeling of Temperature-Dependent Yield Strength in Polycrystalline Ni-Based Superalloys

A new model for the temperature-dependent yield strength of polycrystalline Ni-based superalloys at high strain rates (10(-3) to 10(-4) s(-1)) featuring multimodal precipitate microstructures is presented. It extends existing mean field models based on the summation of particle strengthening and other strengthening contributions, which were originally created to describe behavior at room temperature. Temperature dependence is introduced for each contribution using existing models or datasets from the literature while maintaining physical validity and avoiding unnecessary fitting parameters. Further, the expected change in the precipitate distributions at high temperatures is modeled using CALPHAD. By considering such microstructural changes, the model can predict the yield strength from room temperature to beyond the solvus temperature of the precipitates. Due to the strategy for combining different strengthening contributions, the model can also predict the active deformation modes at any temperature and can be extended easily to incorporate additional deformation mechanisms. The model's sensitivity to microstructural parameters and its strengths and weaknesses are also discussed. Application of the model to three commercial alloys shows good agreement over the whole temperature range.