Grain Boundary Segregation and Embrittlement of Aluminum Binary Alloys from First Principles

TL;DR

This study uses all-electron first-principles calculations to analyze grain boundary segregation and embrittlement in aluminum alloys, emphasizing the importance of considering multiple fracture paths for accurate predictions.

Contribution

It provides a comprehensive reevaluation of grain boundary embrittlement in Al alloys, explicitly comparing fracture paths and methodologies, and offers a large dataset for future research.

Findings

Neglecting low energy fracture paths can cause errors up to 1 eV per solute atom.

Hubbard U DFT effects are minimal for segregation and embrittlement energies in Al(Sc).

The dataset enables comparison between all-electron and pseudopotential methods.

Abstract

Grain boundary segregation controls properties of polycrystalline materials such as their susceptibility to intergranular cracking. It is of interest to engineer alloy chemistry to enhance grain boundary cohesion to prevent intergranular failure. While there is collectively a large first-principles dataset for grain boundary embrittlement in multiple Al-based binary alloys, the methodologies used for the first principles calculations, as well as the analyzed fracture paths, are variable amongst studies. Here, we reevaluate and compute grain boundary segregation and embrittlement from all-electron first-principles for the {\Sigma}5[001](210) Al grain boundary. We explicitly evaluate multiple fracture paths, and provide a study case of the chemical trends of the preferred fracture paths across 69 binary Al alloys. The results suggest that neglecting certain low energy fracture paths can lead to errors of estimating embrittlement potency up to the order of 1 eV per solute atom, especially for multiple d-block transition metal solutes that are of engineering interest. The database calculated here also permits a comprehensive comparison between all-electron and pseudopotential methodologies. The effects of Hubbard U density functional theory on grain boundary segregation and embrittlement in Al(Sc) are found not to be significant in terms of the relative energetic calculations of grain boundaries and free surfaces (differences are of order 0.1 eV or less).