Oxidation Resistance Mechanism of Rare Earth Magnesium Alloy

For the rare earth elements and their corresponding oxides, the electronegativity, Gibbs free energy change of oxidation reaction and the related physical parameters were analyzed. The study on the effect of rare earth elements on the oxidation resistance of magnesium alloys was done from both thermodynamic and kinetic points. The results show that heavier rare earth elements have larger affinity to oxygen than lighter ones; however, any rare earth element presents good affinity to oxygen when compared with magnesium. But the affinity to oxygen of Yb is similar to that of La, Ce etc. It is also found when the molar concentration of earth elements is larger than 0.14 at 1 023 K, the displacement reactions between rare earth elements and MgO could take place. The observations present that the density coefficient of the rare earth oxides is larger than 1 with good protection, except Yb and Eu oxide films. The oxide films can be divided into two layers, i.e. the outer layer is MgO and the interior layer consists of MgO and rare earth oxides, and the latter improve the MgO film loosening and further fill up the voids there, which can efficiently restrain the oxidation of magnesium alloys.