Abstract
The AlB 2 (1 1 1) surfaces and Al (1 1 1)/AlB 2 (0 0 0 1) interface were studied by first-principles calculations to clarify the heterogeneous nucleation potential of α-Al grains on AlB 2 particles in purity aluminium and hypoeutectic Al–Si alloys. It is demonstrated that the AlB 2 (0 0 0 1) surface models with more than nine atomic layers exhibit bulk-like interior, wherein the interlayer relaxations localized within the top three layers are well converged. The outmost layer of AlB 2 free surface having a preference of metal atom termination is evidenced by surface energy calculations. With Al atoms continuing the natural stacking sequence of bulk AlB 2, Al–Al metallic bonds are formed across interface during the combination of Al atoms with Al-terminated AlB 2 surface. The calculated interfacial energy of the Al/AlB 2 interface is much larger than that between the α-Al and aluminium melts, elucidating the poor nucleation potency of α-Al grains on AlB 2 particles from thermodynamic considerations.
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