High temperature oxidation behavior and microstructure evolution of medium Mn steel

The phase transition, microstructure evolution and oxidation behavior of Fe-0.2C-12Mn-3Al-2Cu-xNi steel during the oxidation process for 120 min at 1050°C-1200°C were systematically studied. The twin boundaries will provide rapid channels for the oxygen atoms diffusion, while the (110) and (111) grain orientations show a low oxidation resistance property, which also then promote the oxygen atoms diffuse along grain boundaries. Cu and Ni enrichment areas were formed on the subsurface in the 1100°C-1200°C oxidation stage, which limited the ion diffusion rate on the subsurface and prevented the further growth of the oxide layer. The oxidation temperature, Mn concentration gradient and [CuNi] rich region on the subsurface contribute to multi-oxide layer structure: Mn deficient region, Mn rich region, transition layer and inner oxide layer. The Mn deficient region with rough surface is mainly composed of Fe2O3, Fe3O4 and Mn3O4, while the Mn rich region is mainly composed of FeO and MnO. The honeycomb transition layer and inner oxide layer is composed of FeO, MnO, MnAl2O4, and Al2O3.