Influence of atom termination and stacking sequence on the θ′/Al interfaces from first-principles calculations

• The surface of θ′(001) for Cu-terminated is more stable than that for Al-terminated.
• Interface adhesion for Cu-terminated interface is stronger than that for Al-terminated interface, the hollow site stacking sequence is superior to the top site stacking sequence.
• The Cu-terminated θ′/Al interface with hollow site stacking is the most stable interface.
• Bonding feature and the number of valence electrons are the cause of these differences.

First-principles calculations was used to explore the influence of atom termination and stacking sequence on the interface strength and stability between θ′(Al2Cu) precipitate and Al matrix along experimentally observed orientations, (001)θ′/(001)Al and (010)θ′/(010)Al interfaces. Six interfacial structures were modeled, and work of adhesion, bonding characters, number of valence electrons and thermal stability had been studied. Calculated results revealed that the Cu-terminated interface has larger work of adhesion than Al-terminated interface, and hollow site stacking sequence, with stronger bonding, is superior to top site stacking sequence, adhesion strength for coherent (001)θ′/(001)Al interface is better than that for semi-coherent (010)θ′/(010)Al interface. These differences are attributed to the bonding feature and number of valence electrons. Among the six interface models, the Cu-terminated (001)θ′/(001)Al interface with hollow site stacking has the largest work of adhesion and the smallest interface energy, indicating that it has the best mechanical and thermodynamic properties.

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