中文摘要：

利用SEM、EDAX、XRD等技术分析3种不同Al添加量的镁合金的显微组织和相结构，经实验室模拟金属大气腐蚀实验后观察其腐蚀形貌。结果表明，随着Al含量的增加，Mg-Al合金中β相（Mg17Al12）的数量明显增加；不存在β相的镁合金表面腐蚀产物较少，基体腐蚀较浅，存在β相的镁合金表面腐蚀产物较多，基体出现较深的腐蚀坑；β相的数量与分布的不同是镁合金腐蚀形貌存在差异的主要原因。

英文摘要：

Microstructure and phase constituent of magnesium-aluminum alloys adding different aluminum content （3.4 mass%, 9.3 mass%, 20.7 mass%）were investigated utilizing the scanning electron microscopy （SEM） equipped with energy-dispersive analysis of X-ray（EDAX） and X-ray diffraction （XRD）.The influence of microstructure on the corrosion morphologies was observed after corrosion tests in laboratory simulated atmosphere. The results indicated that magnesium-aluminum alloys with different aluminum content in the atmospheric environment had different corrosion behavior due to amount and distribution of the/3 phase （Mg17TAl12）. Mg-3Al alloy was approximately single-phase alloy,while Mg-9A] alloy and Mg-21Al alloy were two-phase alloys.There were more β phase in Mg-21Al alloy than in Mg-9Al alloy because of its higher aluminum content.Mg-3Al alloy exhibited better atmospheric corrosion resistance than Mg-9Al alloy and Mg-21Al alloy. There were fewer corrosion products on the surfaces of Mg-3Al specimens, while severe corrosion was found to take place in both Mg-9Al alloy and Mg-21Al alloy due to the presence of the β phase in them. More specifically,it was discovered that due to the absence of the couple-actuation of β phase,the corrosion of single-phase alloy Mg-3Al may be attributed solely to the pitting caused by high concentration of Cl^- near the NaCl deposits. However, with Mg-9Al alloy and Mg-21Al alloy,a more important factor for corrosion is the presence of β phase. Under couple-actuation of the negative of β phase, a phase causes a corrosion along the depth extent.