First-principles calculations on Mg/Al2CO interfaces

The electronic structure, work of adhesion, and interfacial energy of the Mg(0 0 0 2)/Al2CO(0 0 0 1) interface were studied with the first-principles calculations to clarify the heterogeneous nucleation potential of Al2CO particles in Mg melt. AlO-terminated Al2CO(0 0 0 1) slabs with seven atomic layers were adopted for interfacial model geometries. Results show that the “Over O” stacking interface is more stable than the “Over Al” stacking interface due to the larger interfacial adhesion and stronger mixed ionic/metallic bond formed across the interface. The calculated interfacial energies of Mg/Al2CO depend on the value of ΔμAl + ΔμC, proving Al2CO particles can exist stably in Mg–Al alloys melt and become effective nucleation substrate for α-Mg grain under certain conditions. The above calculation and corresponding analysis provide strong theoretical support to the Al2CO nucleus hypothesis from interfacial atomic structure and atomic bonding energy considerations.