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

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.