First-Principles Investigation of the Interfacial Stability, Precipitate Formation, and Mechanical Behavior of Al₃Li/Al₃Zr/Al Interfaces

Precipitates including Al₃Li, Al₃Zr and core–shell structured Al₃Li (Al₃Zr) produce significant strengthening effects in Al-Li alloys by means of anti-phase boundaries and dislocation looping. However, the precipitate/metal interfacial structures and precipitate formation mechanisms in Al-Li alloys remain unclear due to the lack of advanced experimental methods. In this work, atomic-scale structural models of Al₃Li/Al, Al₃Zr/Al, and Al₃Li/Al₃Zr interfaces are created, while bridge-, top-, hollow-, and center-stacking sequences are applied, respectively. Within these models, Al slabs with 5 atom layers and Al₃Li and/or Al₃Zr slabs with 6 atom layers are selected in which interfacial orientations of (100), (110), and (111) are considered. For the Al₃Li/Al, Al₃Zr/Al, and Al₃Li/Al₃Zr interfaces, the structural models with bridge- and hollow-stacking sequences generate the most stable energy-based interfaces. Moreover, the nucleation free energies of the core-shell structured Al₃Zr(Al₃Li) are larger than those of the isolated Al₃Li+Al₃Zr and core-shell structured Al₃Li(Al₃Zr), leading to the absence of the core-shell structured Al₃Zr(Al₃Li) in most experimental observations. Further studies of the uniaxial tensile mechanical properties of the Al₃Li/Al, Al₃Zr/Al, and Al₃Li/Al₃Zr interfaces revealed that the Al₃Zr/Al interfaces possess larger Young’s moduli and tensile strengths than those of the Al₃Li/Al and Al₃Li/Al₃Zr interfaces. In conclusion, the interfacial stability, precipitate formation and mechanical behaviors of Al₃Li/Al₃Zr/Al interfaces are elucidated for the development of Al-Li alloys and their composites.