在分析2024铝合金FSW焊缝表面组织及析出相种类的基础上，采用腐蚀类原位观察揭示了焊缝表面的腐蚀演变行为，结合透射电镜、示差扫描量热分析及电化学分析对焊缝接头的腐蚀机理进行了探索。结果表明：FSW后，焊缝区的耐蚀性能下降，SAZ腐蚀最严重，点蚀的起源为S相。焊缝区晶体缺陷增加，导致晶粒和晶界在电化学性能上的不均匀性增大。在FSW过程中SAZ的S相粒子被打碎，并发生部分回溶。当腐蚀发生时，被打碎的S相加大了 SAZ的点蚀密度；溶入基体的Mg元素，提高了轴肩作用区的活性。
In this paper, based on the analysis to surface microstructure of FSW AA2024 joint, the corrosion evolution behavior was revealed by a quasi-in-situ observation method. Besides, the corrosion mechanism of the FSW joint was investigated by combining TEM, DSC and electrochemical analysis. The results show that FSW makes the corrosion resistance decrease, which is characterized by the facts that the most corrosion in the SAZ (shoulder active zone) and the pitting corrosion initially originates in dissolving of the $S$ phase (Al2CuMg). TEM observations indicate that crystal defects density increases in the welded joints causing the more different electrochemical properties between grains and grain boundaries. The S phase particles are broken and partially redissolved during the FSW process in the SAZ. When the corrosion happens, the broken S phase particles increase the pitting corrosion density of the SAZ. In addition, the activity of the SAZ is enhanced due to the doped Mg.
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