Research On The Oxidation Behavior Under High Temperature In The Air And Corrosion Resistance Of Mg-li Alloys

Magnesium-lithium alloy is a kind of engineering metallic material with a minimumdensity, and it possesses a high strength and good electromagnetic shielding performance, etc.The alloy meets the requirements of environmental protection, energy conservation andemissions reduction. Therefore, it has been widely used in electronics and aerospace industry.However, the application of Mg-Li alloy is seriously restricted by the poor resistance of hightemperature oxidation and corrosion. Taking LAZ532, LAZ832and LAZ1432alloy as theresearch object, the influence of adding rare earth Y into Mg-Li alloys and the oxidationmechanism at elevated temperature and corrosion are discussed in this dissertation.In this paper, we studied the structure and composition of Mg-Li alloy surface before andafter oxidation by using metallographic microscope, SEM, EDS, XRD and XPS. By usingDSC, we concluded the typical oxidation kinetics curves of three typical alloys at elevatedtemperature. It is found that the surface morphology of LAZ532and LAZ832alloy that areoxided at elevated temperature is bubble-like structure, which is consisted of Li2CO3, MgCO3and Al2O3. LAZ1432alloy surface oxidation film can be divided to two layers. The outerlayer is composed of Li2CO3and Al2O3, and the inner layer is composed of spinel (MgAl2O4)which possesses a more stable thermal expansion coefficient. Due to the existence of thespinel structure, the oxidation resistant performance at elevated temperature of LAZ1432alloy is better than that of LAZ532and LAZ832alloy. But this spinel structure has no effecton alloy corrosion resistance with a long-term issue. With the long-term issue, the corrosionresistance of the three alloys mentioned above without oxidation is better than that afteroxidation.The chemical composition of oxide on the surface of LAZY alloys generated at elevatedtemperature is similar to that on LAZ alloys. And rare earth Y can effectively improve theadhesion strength of the oxide film, which is not easy to fall away from the alloy surfaceaccordingly. Rare earth Y can effectively improve the oxidation resistant performance of thealloy, but it can not effectively improve the corrosion resistance of the alloy.The dynamics curve for oxidation of the alloy shows that oxidation films on the surfaceof the alloy generate under the condition of elevated temperature have certain protectiveeffect.