Unveiling the Oxidation Behavior of a Binary Mg–Y Alloy

ABSTRACT Magnesium and its alloys are the most promising lightweight metallic materials because of their outstanding mechanical performance. However, Mg alloys have long been criticized for their low oxidation resistance. In this study, the isothermal oxidation of a Mg–Y alloy at 350°C was investigated, and the resulting oxide scale was systematically characterized using an optical microscope, scanning electron microscope (SEM), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), and other analytical techniques. The findings reveal that isothermal oxidation results in (i) an increase in the average Y content along grain boundaries, from 1.41 to 3.05 at.%, and surface enrichment of Y content from 0.86 to 3.07 at.% after 6 to 48 h of oxidation; (ii) inhomogeneous oxidation caused by microstructural heterogeneity; and (iii) the formation of an oxide scale consisting of a mixture of MgO and oxygen‐deficient Y₂O₃ at the oxide/substrate interface, driven by the inward transport of oxygen anions. The molar ratio of MgO to Y₂O₃ was found to vary with oxidation time.