Magnesium alloy is a structural material with low density and high specific strength, which has received widespread attention in the fields of transportation vehicles and consumer electronics. In magnesium alloys containing rare-earth element Y, dense rare-earth oxide films are formed at high temperatures, which can retard the diffusion of oxygen to the metal, thereby improving the flame retardancy of the alloy. Mg-Gd-Y-Zn-Zr alloy is an important high-strength and heat-resistant magnesium alloy variety, and it is the current research focus of rare-earth magnesium alloys.
After the Mg-Gd-Y-Zn-Zr alloy was heat-treated, Wu Luoyi of Hunan University School of Materials Science and Engineering observed the formation of a LPSO-free layer with a thickness of less than 50 μm under the protective rare earth oxide scale. According to the morphology and distribution of the LPSO phase, the heat-treated sample can be divided into 4 regions: rare earth oxide scale, LPSO-free layer, lamellar LPSO layer, and bulk LPSO region (inside the material). The researchers used the theory of selective oxidation of alloying elements to explain the formation mechanism of complex microstructures on the sample surface. The research on the corrosion behavior of the T6 alloy shows that the rare earth oxide scale and LPSO-free layer existing on the surface significantly improve the corrosion resistance of Mg – Gd – Y – Zn – Zr alloys.