中性盐雾下7075铝合金搅拌摩擦焊焊缝的腐蚀行为

用金相和透射电镜对包铝的7075铝合金搅拌摩擦焊接头组织和微结构进行分析，用中性连续盐雾试验研究焊缝表面的腐蚀行为，并观察焊缝宏观和微观腐蚀形貌。研究结果表明：焊缝区的晶粒和第二相粒子得到明显细化，在焊缝表面的第二相粒子分布不均匀；搅拌摩擦焊焊缝区耐蚀性比包铝的母材低。腐蚀首先从局部点蚀和晶间腐蚀开始，最终演变为剥落腐蚀。

CORROSION BEHAVIORS OF FRICTION STIR WELDED JOINT OF 7075 ALUMINUM ALLOYS UNDER NATURAL SALT SPRAY

The microstructure of friction stir welded (FSW) joint of 7075 aluminum alloy were examined by using of optical microscope and transmission electron microscope. The corrosion behaviors of the joint were investigated by method of natural salt spray. The macroscopical and microscopical appearances of the weld seam were observed by using of scanning electron microscope after corrosion test. The results show that the size of the grain and the second phase particles in the weld zone has been obviously refined. The distribution of the second phase particles are not homogeneous on the weld seam surface. The resistance to corrosion of FSW seam is lower than that of base metal enveloped with pure aluminum layer. The corrosion styles during the initial stage are mainly local pitting and intergranular corrosion and develop to exfoliation corrosion after long time corrosion.