中文摘要：

利用OM、SEM和电化学工作站分析了LY12铝合金搅拌摩擦焊焊缝组织及其在3.5%NaCl溶液中的极化曲线和腐蚀形貌,研究了焊缝的腐蚀性能。结果表明：母材、热影响区和热力影响区的第二相尺寸较大,部分超过10μm,而轴肩作用区的第二相尺寸较小、数量少且分布均匀,焊核区的第二相尺寸与轴肩作用区类似,但焊核区有第二相沿洋葱环组织集中析出。轴肩作用区、焊核区、热影响区和热力影响区的腐蚀电位依次负移,电流密度增大。热影响区和热力影响区、焊核区、轴肩作用区的腐蚀程度逐渐降低,焊缝区的腐蚀程度从上而下逐渐增加,热影响区和热力影响区从上而下腐蚀程度逐渐减小,返回边的耐蚀性优于前进边。第二相的尺寸和分布情况是影响焊缝耐蚀性的主要因素。

英文摘要：

Microstructure,corrosion morphology and polarization curves in 3.5% NaCl solution for LY12 aluminum alloy friction stir welding were investigated using OM,SEM and electrochemical workstation and the corrosion properties were studied.The results showed that the size of the second phase in BM,HAZ and TMAZ was the largest,some more than 10μm.The amount and size of the second phase in SDZ was smallest and evenly distributed.The second phase in Nugget zone was similar in size to SDZ and someone precipitated intensively.The corrosion potential of the SDZ,the Nugget zone,HAZ and TMAZ shift negatively,and the current density increases orderly.The extent of corrosion in the SDZ,the Nugget zone,HAZ and TMAZ reduced gradually.The extent of corrosion in the weld center gradually increased from top to bottom,and gradually reduced in HAZ and TMAZ from top to bottom.The corrosion resistance of HAZ and TMAZ in advancing side of the welded was smaller than the ones in retreating side.The size and distribution of the second-phase caused the difference of corrosion resistance in the various regions for the joints.