本论文以AZ31B镁合金搅拌摩擦焊和激光焊接头为研究对象，选用磷酸盐电解液体系，在AZ31B镁合金搅拌摩擦焊和激光焊样品表面制备了一层微弧氧化陶瓷膜，分析了接头不同区域膜层特性，评估了微弧氧化表面处理对焊接接头应力腐蚀开裂行为的影响。另外还通过向电解液中加入不同浓度的ZrO2微粉，研究ZrO2微粉添加剂对镁合金微弧氧化膜致密性的影响。原子发射光谱、XRD、EDS以及XPS结果表明，电解液中元素都参与了微弧氧化膜的生长过程。微弧氧化膜主要由MgO和MgF2相组成。AZ31B镁合金搅拌摩擦焊（FSW）接头不同区域的晶粒大小和均匀性差别很大，导致膜层表面形貌与致密性有所不同但差别不大。AZ31B镁合金搅拌摩擦焊接头母材区的耐腐蚀性能最好，其次是焊核区，而热影响区的耐腐蚀性能最差；而AZ31B镁合金激光焊的焊核区耐腐蚀性能略好于母材区，微弧氧化表面处理大大提高了AZ31B镁合金焊接接头的耐腐蚀性能。AZ31B镁合金母材、激光焊和搅拌摩擦焊工件在空气中都为塑性断裂机理，在ASTM1384标准的溶液中应力腐蚀为脆性断裂机理。微弧氧化处理可以提高镁合金及其焊缝在应力腐蚀中的耐蚀性，但是膜层破损后断裂机理与未微弧氧化的AZ31B合金一致，通过监控应力腐蚀测试过程中AZ31B拉伸试样的自腐蚀电位能够预测金属将要发生应力腐蚀断裂。电解液中添加ZrO2微粉后，镁合金微弧氧化膜中除MgO外，还出现四方相t-ZrO2、少量的单斜相m-ZrO2和K3ZrF7，主要集中在外部疏松层里。ZrO2微粉的加入，使微弧氧化膜层显微硬度升高，粗糙度有所降低。电解液中添加ZrO2粉后，微弧氧化膜的耐腐蚀性能得到提高。添加2g/L ZrO2粉时制备的微弧氧化膜耐腐蚀性能最佳。

The microarc oxidation (MAO) coatings were prepared on friction stiring welded (FSW) and laser welded joints of AZ31B magnesium alloy in phosphate electyrolyte. The properties of MAO coatings in different zones of joints were compared, meanwhile the stress corrosion crack (SCC) of welded joints before and after MAO surface treatment was evaluated. In addition, we studied the effect of ZrO2 nanoparticle additive into electrolyte on the compactness of MAO coatings of AZ31B magnesium alloy.The results of OES, XRD, EDS and XPS analyses showed that elements in the electrolyte were participated in the growth processes of MAO coatings. The coatings were composed mainly by MgO and MgF2 phases.It was found that the grain size and microstructure in different zones of FSW joints had a little difference in the morphology and compactness of coatings. The base metal (BM) of FSW joints had the best corrosion resistance comparing to the stirring zone (SZ) zone and heat affected zone (HAZ). The corrosion resistance of welding zone (WZ) zone of laser welded joint was a little better than BM zone. So the MAO treatment could greatly improve the corrosion resistance of welded joints of AZ31B magnesium alloy.The fracture mechanism of FSW welded and laser welded joints of AZ31B magnesium alloy was plastic fracture in air and brittle fracture in ASTM 1385 solution. The MAO treatment could improve the SCC corrosion resistance of welded joints of AZ31B magnesium alloy. But the fracture mechanism before and after MAO surface treatment was almost same after the rupture of coatings. By monitoring the natural potential of SCC process, we could predict failure behaviors of magnesium alloy before it happens.With adding ZrO2 nanoparticles into electrolyte, the MAO coating of AZ31B magnesium alloy was mainly composed by MgO. Meanwhile, t-ZrO2, m-ZrO2 and K3ZrF7 phases were also found, which were found in the outer layer. The incorporation of ZrO2 nanoparticles had caused the increase of microardness and the decrease of roughness, then the corrosion resistance of MAO coatings containing ZrO2 phase was improved. It was found that the additive of 2g/L ZrO2 nanoparticles fabricated the MAO coating with excellent compactness on AZ31B magnesium alloy.