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.