A ReaxFF molecular dynamics study of the micro-dynamic oxidation behavior of Ni-Al alloys

Abstract

Revealing the oxide-formation process at the atomic scale is challenging but extremely important for explaining the oxidation mechanism of an alloy. In this study, the microscopic dynamic oxidation behavior of nickel-based high-temperature alloys was simulated using reactive-force-field molecular dynamics. Adsorption was found to first occur in the vicinity of the Al atoms, which detach more readily from the surface of the alloy than the Ni atoms, giving rise to an uneven oxide-film distribution, surface stresses, and high-stress areas in the vicinity of Al. Outer-oxide growth mainly occurs through the outward diffusion of Al atoms, while the bond-distribution data reveal that the oxide is an intermediate state and that longer oxidation times only result in the transfer of charge from Al to O. Ni atoms were found to survive jumping at high temperatures, while surface roughness increased leading to oxygen atoms that are more inclined to diffuse into the interior of the alloy.