Grain boundary segregation in Ni-base alloys: A combined atom probe tomography and first principles study

Grain boundary engineering (GBE) plays an important role in the design of new polycrystalline materi-als with enhanced mechanical properties. This approach has been shown to be very effective in design of Ni-base alloys, where grain boundary segregation is expected to play a central role in defining their mechanical behavior. In the present work, we apply a powerful combination of advanced experimental and theoretical methods to reveal the grain boundary chemistry of the 725 Ni-base alloy at the atomic level. The methods of investigation comprise atom probe tomography (APT) measurements and density functional theory (DFT) calculations. We also propose a way to cross-validate DFT and APT results in a DFT-based model approach for evaluation of the interfacial excess as a function of the heat treatment history of the material and its chemistry. Both theoretical and experimental methods are applied to a detailed analysis of the GB chemistry of three modifications of the 725 alloy and the results of this in-vestigation are presented and discussed in detail. (c) 2021 The Authors. Published by Elsevier Ltd on behalf of Acta Materialia Inc. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )

Automated summary

Grain boundary engineering is crucial in designing new materials, especially for nickel-based alloys. By combining advanced experimental and theoretical methods, the grain boundary chemistry of the 725 Ni-base alloy is revealed, providing a way to evaluate the interfacial excess based on the material's heat treatment history and chemistry.