Molecular dynamics-based characterisation of early oxide in Fe/Cr alloys

The addition of Cr is known to work as an effective prevention against oxidation in Fe-based alloys. This can be attributed to the peripheral oxide, the structure of which is dependent on the composition of the alloy. Using Molecular Dynamic (MD) calculations with a Reactive Force Field (ReaxFF) potential, we successfully identify several oxide structures arising during initial oxide formation in [100] Body-Centered Cubic (BCC) Fe1−xCrx alloys. This structure was found to differ between the surface and bulk. Further, by gradually increasing the Cr content, we manage to track the structural Cr-dependence of both the bulk- and the surface oxide. Both in the surface and bulk, phase changes in the oxide are observed as the Cr content increases. At the surface, this takes place at around 30%–50% Cr. In the bulk, it takes place at around 30% and 70% Cr.