7075铝合金FSW焊接接头在海水中的腐蚀演化行为

Corrosion Evolution Behavior of 7075 Aluminum Alloy FSW Welded Joints in Seawater

通过形貌观察、极化曲线分析、加速腐蚀试验等,研究了7075铝合金搅拌摩擦焊(FSW)焊接接头各区域及其母材在模拟海水中的全过程腐蚀机理。结果表明:该焊接接头各区域及其母材不同的显微组织和第二相是决定其腐蚀形貌特征和耐蚀性不同的主要原因;随着腐蚀时间的延长,焊接接头各区域的腐蚀损伤按照点蚀-晶间腐蚀-剥落腐蚀的顺序演变,并循环往复进行;该FSW焊接接头各区域的海水腐蚀损伤程度均高于母材,且热影响区(HAZ)在腐蚀过程中的腐蚀损伤程度最重,是FSW焊接接头耐蚀性最差的区域。

The entire corrosion mechanism of various regions and their parent materials of 7075 aluminum alloy FSW welded joints in simulated seawater was studied by observing the morphology,analyzing polarization curves,and conducting accelerated corrosion tests.The result showed that the different microstructures and second phases of various areas of the welded joints and their parent materials were the main reasons for their different corrosion morphology characteristics and corrosion resistance.With the prolongation of corrosion time,the corrosion damage in each area of the welded joint evolved in the order of pitting corrosion,intergranular corrosion,and exfoliation corrosion,and proceeded in a cyclic manner.The seawater corrosion damage degree of each area of the welded joint was higher than that of the base metal,and heat-affected zone(HAZ)had the worst corrosion damage during the corrosion process,which was the area with the worst corrosion resistance of the welded joint.