In-Situ Atomic-Scale Imaging on Oxidation of Magnesium
34 Pages Posted: 6 Nov 2018
Date Written: November 2, 2018
Abstract
Understanding oxidation process of Mg has great implications to improve mechanical/corrosion properties of Mg alloys. The oxide growth process of a single crystal Mg has been investigated by in-situ atomic-scale aberration-corrected environmental transmission electron microscopy. The oxidation process of Mg mainly proceeds through two different pathways: the outward expansion growth of MgO and the inward migration growth of MgO/Mg interface. The inward migration growth rate of MgO/Mg interface is about seven times than that of the outward expansion growth of MgO along the same orientation plane. Both growth rates are anisotropic, relative to orientation planes. The (011 ̅0)Mg||(020)MgO interface exhibits about twice rate than the (0002)Mg||(200)MgO interface. The inward migration growth is composed of three steps: the arriving of oxygen atoms to MgO/Mg interface, the oxygen adsorption in MgO/Mg interface and the oxygen diffusion in the core Mg. Three inward oxidation steps are elucidated in terms of high revolution transmission electron microscopy observations and theoretical calculations. The results demonstrate that the origin of inward anisotropic oxidation is mainly related to different oxygen diffusion barriers along altered crystallographic planes.
Keywords: Magnesium, Oxidation, In-situ, Atomic simulations, DFT calculations
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