Modeling complex diffusion phenomena in Ni-based superalloys under composition gradient

The idea of compositionally-graded alloys, as a subgroup of Functionally Graded Materials (FGMs), consists of, for example, additively fabricated parts, coatings, and welded dissimilar alloys. Understanding and predicting diffusion events as interdiffusion of elements/vacancies, phase transformations, Kirkendall voids etc.. in these alloys are significantly important in science and industry.

The present work consists of modeling various complex diffusion-related phenomena in single-crystal Ni-based superalloys including CMSX-10 and CMSX-4, under isothermal annealing and composition gradient. The simulated diffusion events include multi-component diffusion of elements and vacancies, phase transformations, dissolution of precipitates and Kirkendall pores nucleation, growth and their morphological instability.

The applied methodology combines novel quantitative phase-field models coupled with thermodynamic and atomic mobility parameters based on the CALPHAD approach.

For all simulated efforts, the achieved results are compared with experimental data such as interdiffusion profiles, SEM analysis of microstructure and synchrotron X-ray tomography of the Kirkendall pores.