中文摘要：

AZ91D镁合金在温度40 ℃和相对湿度100%RH的大气环境中, 其初期大气腐蚀符合指数衰减规律, 在高温高湿环境中促进了AZ91D镁合金大气腐蚀的发展. AZ91D镁合金的大气腐蚀初期腐蚀产物变化规律： 基体上出现点刺状腐蚀产物, 点刺状腐蚀产物长大后形成团刺状的腐蚀产物. 团刺状的腐蚀产物不断长大, 相邻近的团刺状的腐蚀产物聚集交织在一起, 构成疏松的腐蚀产物形貌. 这种疏松的腐蚀产物形貌不具备保护作用, 使得大气腐蚀不断加快. 通过对AZ91D镁合金的腐蚀产物的EDX能谱分析, 并结合对腐蚀产物形貌的观察, 表明在大气腐蚀初期的腐蚀产物主要为： 初期形成的MgO和随后形成更加稳定Mg（OH）2. AZ91D镁合金在β相、划痕和晶界等附近区域容易发生腐蚀. 同时表面残留的污染物（手的汗迹等）区域更加容易发生腐蚀.

英文摘要：

The behaviors of the initial stages of atmospheric corrosion for AZ91D magnesium alloys at 40 ℃and 100% RH were investigated. The kinetics of atmospheric corrosion is found to obey the rule of exponential decay. The higher of temperature and higher of humidity accelerate and catalyze the reaction of initial stages of atmospheric corrosion for AZ91D magnesium alloys. The evolvement law of corrosion products is shown that particle corrosion products firstly form on the surface, and then particle corrosion products grow agglomerate with branches and assemble each other.The corrosion products are loose and have not protective effect. The morphologies were observed by scanning electron microscopy （SEM）, and Energy Dispersive X-ray Detector （EDX） was used to analyze the corrosion products. There are MgO corrosion products in the initial stages, and then Mg （OH）2 corrosion products are more steadier. The β phases, nicks and crystal boundaries are main localities which are easy corrosion in the initial stages, moreover the contamination on the surface of AZ91D magnesium alloys are serious corrosion localities.