Microstructure of corrosion product film formed on aged WE43 alloy
(1. School of Materials Science and Engineering, University of Science and Technology of China, Shenyang 110016, China;
2. Shi-changxu Innovation Center for Advanced Materials, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China;
3. School of Materials Science and Engineering, Shandong University of Science and Technology, Qingdao, Shandong 266590, China)
2. Shi-changxu Innovation Center for Advanced Materials, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China;
3. School of Materials Science and Engineering, Shandong University of Science and Technology, Qingdao, Shandong 266590, China)
Abstract: A dense three-layer corrosion product film was formed on aged WE43 alloy in 3.5 wt.% NaCl solution. The microstructure of the film was analyzed in detail by TEM. The three-layer corrosion product film is composed of RE2O3, MgO layer doped with RE2O3 and Mg(OH)2 layer doped with RE2O3 from the inside to the outside. A large amount of rare earth oxide particles formed both by the outward oxidation of rare earth precipitates and rare earth elements, are the main reason for the formation of the corrosion film. The RE2O3 has the preferential orientation with ( 1402'''' type="#_x0000_t75"> 11) plane and [231] direction parallel to (002) plane and [ 14011'''' type="#_x0000_t75"> 0] direction of MgO, respectively. Thus, the rare earth oxide particles can fill the gap of porous MgO layer, and improve the compactness of the film. The inner RE2O3 layer and mixed layer of MgO and RE2O3 play an important role in the formation of the film. The compact inner film can prevent the corrosion medium from reacting with the Mg matrix.
Key words: magnesium alloy; corrosion product film; HRTEM; precipitate; oxidation