铝/铜异种金属搅拌摩擦焊接头腐蚀行为研究

Study on Corrosion Behavior of Friction Stir Welded Joints of Aluminum/Copper Dissimilar Metals

采用搅拌摩擦焊接技术实现了3 mm厚6061-T6铝合金与T2紫铜的焊接,研究了Al/Cu搅拌摩擦焊接头的宏观成形、电化学腐蚀以及浸泡腐蚀行为。结果表明,Al/Cu搅拌摩擦焊接接头成形良好,未见裂纹、孔洞等缺陷。Cu的腐蚀电位高于Al,导致Al/Cu之间形成宏观电偶。Al/Cu接头的腐蚀电位低于两种母材,腐蚀电流密度大于两种母材,接头中的宏观电偶效应加速了接头的腐蚀。在浸泡24 h内,接头的腐蚀主要发生在铝合金侧,其中铝侧热影响区的腐蚀最严重,形成的点蚀坑尺寸较大。铝侧焊核区和铝母材也发生了局部点蚀,腐蚀程度相对较轻。铝侧表面腐蚀产物为Al(OH)3/Al2O3。

The welding of 6061-T6 aluminum alloy with thickness of 3 mm and T2 pure copper was realized by friction stir welding technology.The macro forming,electrochemical corrosion and immersion corrosion behaviors of the Al/Cu joints were investigated.The results show that the Al/Cu friction stir welding joint is well formed,and no cracks,holes and other defects are observed.The corrosion potential of Cu is higher than that of Al,leading to the formation of macroscopic galvanic couples between Al/Cu.The corrosion potential of the Al/Cu joints is lower than that of the two base metals,and the corrosion current density is greater than that of the two base metals.The macroscopic galvanic effect in the joints promotes the corrosion of the joints.Within 24 h of immersion,the corrosion of the joint mainly occurs on the aluminum alloy side,among which the corrosion of the heat affected zone on the aluminum side is the most serious,resulting in larger corrosion pits.Local pitting corrosion also occurs in the nugget zone of aluminum side and the aluminum base material,with a relatively light of corrosion.The corrosion products on the aluminum surface is Al(OH)3/Al2O3.