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采用氯化钠+过氧化氢溶液浸泡试验研究AA6061-T6铝合金搅拌摩擦焊搭接接头的腐蚀行为。采用循环动电位极化测试、扫描电子显微镜和能谱仪表征腐蚀形貌,揭示焊接区与基体合金的腐蚀机理。研究了焊接接头的显微组织和剪切强度。结果表明,与基体合金相比,焊接区在腐蚀溶液中会发生晶间腐蚀和点蚀。搭接剪切测试结果表明,所得焊接接头的拉伸剪切强度为128 MPa,超过基体合金强度的60%。电化学测试结果表明,焊核区和热影响区的保护电位比点蚀电位更负,说明焊核区与热影响区点蚀的趋势不强。基体合金抗腐蚀性比焊缝区的强,而热影响区的抗腐蚀性最差。点蚀主要源于金属间化合物边缘,因为与铝基体相比,金属间化合物的自腐蚀电位更高而成为阴极。由于焊缝区的金属间化合物增加,腐蚀电偶增加,焊缝的抗腐蚀性降低。
The corrosion behavior of AA6061-T6 aluminum alloy friction stir welded lap joint was studied by using sodium chloride + hydrogen peroxide solution immersion test. Cyclic potentiodynamic polarization test, scanning electron microscopy and energy dispersive spectroscopy were used to characterize the corrosion morphology. The corrosion mechanism of the weld zone and the matrix alloy was revealed. The microstructure and shear strength of welded joints were studied. The results show that compared with the base alloy, the weld zone intergranular corrosion and pitting corrosion occurs in the solution. Lap shear test results show that the resulting welded joint tensile shear strength of 128 MPa, more than 60% of the base alloy strength. The electrochemical test results show that the protective potential in the nugget and heat affected zone is more negative than the pitting potential, indicating that the tendency of pitting corrosion in the nugget and heat affected zone is not strong. The corrosion resistance of the matrix alloy is stronger than the weld zone, while the corrosion resistance of the heat affected zone is the worst. Pitting is mainly due to the edge of the intermetallic compound because the intermetallic compound has a higher self-corrosion potential than the aluminum matrix and becomes the cathode. Due to the increase of intermetallic compounds in the weld zone, the corrosion resistance increases and the corrosion resistance of the weld decreases.