The role of vacancy in alloyed (001)α-Al//(001)θ' interface

The effects of a vacancy on the chemical bonding strength of the (001)α-Al//(001)θ' interface were systematically investigated by using the first-principles calculations. The migration energy barrier of a single vacancy around the Sc/Zr/Cd was calculated to assess the hindering effect of the Sc/Zr/Cd on the vacancy migration. Results suggest that a vacancy enhances the chemical bonding strength of the Sc/Zr-alloyed interface, which is attributed to the high electron localization level between Sc/Zr and its nearest-neighbor host atom Al at atomic layer 2 and between Al atoms at atomic layer 1 and significant charge accumulation in the interface. The introduction of a vacancy will weaken the magnitude of the chemical bonding strength reduction of Cd-alloyed interface, which is ascribed to the large electron localization level between Al atoms at atomic layer 1 and significant charge accumulation in the interface. The migration energy barrier of a vacancy around Sc/Zr/Cd at the Sc/Zr/Cd-alloyed interface is much larger than those around Al at the pure interface, indicating that Sc/Zr/Cd has a hindering effect on the vacancy. Although Cd shows a detrimental effect on the chemical bonding strength of the interface, it has a strengthening effect by hindering the vacancy migration.