2219铝合金搅拌摩擦焊接接头剥落腐蚀机理

采用原位腐蚀试验、静态失重试验、浸泡试验研究了2219铝合金搅拌摩擦焊接接头的剥落腐蚀行为与机理。结果表明:2219铝合金搅拌摩擦焊焊缝腐蚀速率比母材小,焊缝的抗腐蚀性提高;腐蚀从局部点蚀开始,起源于第二相粒子与其边缘的铝基体,第二相粒子作阴极;原位腐蚀2 h后焊核与热机影响区发生晶间腐蚀,母材发生严重的点蚀;均匀分布的第二相粒子与细小的等轴晶组织是焊核区剥落腐蚀敏感性降低的主要原因。

Exfoliation Corrosion Mechanism of Friction Stir Welded 2219 Aluminum Alloy

The corrosion behavior and mechanism of friction stir weld (FSW) joint of 2219 aluminum alloy was investigated by in-situ corrosion test, static mass loss test and immersion test. The results show that the corrosion rate of the weld is less than that of the parent material and the corrosion resistance of the weld improves greatly. The local pitting corrosion initially originates in dissolving of the adjacent matrix around the second phases and the second phase particles act as cathode. The intergranular corrosion happens in the weld nugget zone (WNZ) and thermo-mechanically affected zone (TMAZ) after in-situ corrosion test for 2 h and pitting corrosion occurs in base materials. The homogeneous second phase particles and fine equiaxed grains in the WNZ are the main reasons for the high resistance of exfoliation corrosion.