Effect of oxidation time on the composition and structure evolution of the oxide film on Al-Mg-Sc-Zr alloy

Abstract

The oxidation behavior of Al-Mg-Sc-Zr alloy at 300 °C for different oxidation times was systematically studied, the influence of oxidation time on the composition of the oxide scale and the microstructure of the substrate was revealed, and the relationship between oxidation time, microstructure of substrate and oxide scale composition and structure was established. The results showed that with the increase of oxidation time, the morphology of the oxide scale changed from irregular and thin film to a loose structure oxide scale with MgO particle aggregates, and finally formed a thick and dense oxide scale. Initially, Al₂O₃ dominated the oxide scale composition, but with increasing oxidation time, the MgO content gradually increased. At 1.5h, the MgO content in the oxide scale exceeded that of Al₂O₃, eventually becoming the predominant component. And at 2.0 h, the composition of the oxide scale changed to MgO, MgAl₂O₄, and a few Al₂O₃, and MgAl₂O₄ was present largely in the deep part of the oxide scale, gradually replacing MgO in the thickness direction as the oxidation time prolonged. At the same time, the orientation of the matrix grains changed, and the proportion of HAGBs increased dramatically, which increased the diffusion rate of Mg atoms. As the oxidation time increased, changes in dislocation density and precipitation of nanoparticles also affected the path and speed of atomic migration, thereby determining the phase composition and structural stability of the oxide scale on Al-Mg-Sc-Zr alloy.