Segregation of alloying elements to stabilize θ′ phase interfaces in Al-Cu based alloys

Interactions of alloying elements (Si, Mg, Mn, Zr, Zn) and vacancies with coherent interfaces of theta' phase in Al-based alloys have been systematically studied by means of ab initio supercell calculations. The interface structure with a half-filled interfacial Cu layer is calculated to be lower in energy (by 0.1 eV per structural vacancy) than the structure with a filled Cu layer; the degree of interface reconstruction depends on the availability of vacancies. The presence of vacancies in the interfacial Cu layer plays a crucial role in the interaction of solutes with coherent theta' phase interfaces. The solute-interface interaction energies are calculated to be much weaker for elements having closed (Cu, Zn) or empty (Mg, Si) d-electron shells than for d-transition metals (Mn, Zr). To clarify the roles of alloying elements and interface structure in the stability of theta' phase precipitates, we analyze the solute-interface interactions in terms of electronic-structure and atomic-size contributions to interatomic bonding. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

The study systematically investigated the interactions of alloying elements and vacancies with coherent interfaces of the theta' phase in Al-based alloys, revealing that the presence of vacancies in the interfacial Cu layer plays a crucial role in solute-interface interactions. The solute-interface interaction energies were found to be weaker for elements with closed or empty d-electron shells compared to d-transition metals. The roles of alloying elements and interface structure in the stability of theta' phase precipitates were analyzed in terms of electronic structure and atomic size contributions to interatomic bonding.