Unveiling initial oxidation behavior of Mg-Y-Zn long-period stacking ordered (LPSO) phase

Abstract

The oxidation of long-period stacking ordered (LPSO) phase has received little attention. The present work reveals the inherent oxidation behavior of Mg-Y-Zn LPSO phase at initial stage through detailed microstructural analysis and thermodynamic calculations. At a relatively low temperature (350 oC), Y2O3 is the only oxidation product at the alloy surface, which shows a preferential nucleation and lateral growth behavior. Meanwhile, an underlying Mg-rich layer incorporated with Y-rich particles appears as a decomposition product of the LPSO phase. At a high temperature (500 oC), the long-range Y transport is dynamically suppressed by the thick Mg-rich shielding layer, prompting the preferential formation of MgO rather than Y2O3 at the growth front. The present study would contribute to the development of oxidation-resistant LPSO-containing Mg alloys.