Adhesion strength, interfacial bonding, and fracture mechanism of the Mg/Ti2AlC interface from first-principles calculation

In Mg matrix composites, the interface between Ti2AlC and Mg plays a vital role in the strengthening mechanism and fracture process. Using first-principles calculations, a systematic analysis is carried out for the atomic structures, work of adhesion, interfacial energy, chemical bonding of the Mg(0001)/Ti2AlC(0001) coherent interface. The results of the relaxed interface structure show that, for all the interface studied, the bridge site (MT) configurations are unstable and convert into the hollow site (HCP1 or HCP2) configurations. Moreover, the work of adhesion and interfacial energy measurements reveal that C-HCP2 configurations are more thermodynamically stable. Furthermore, due to the formation of a strong Mg–C covalent bond across the interface, the electronic structure studies indicate that the C-terminated Mg(0001)/Ti2AlC(0001) interface is more thermodynamically stable. The Al-, Ti(C)-, and Ti(Al)-terminated interfacial fractures are found to initiate at the Mg/Ti2AlC interface, whereas the C-terminated interfacial fracture could initiate in the Mg bulk phase.