2219铝合金母材及焊接接头的腐蚀行为

Corrosion Behavior of 2219 Aluminum Alloy Base Metal and Welding Joints

采用剥蚀试验和动电位极化曲线测试对2219铝合金母材、搅拌摩擦焊(FSW)和钨极氩弧焊(TIG)焊接头的腐蚀行为进行了研究。通过腐蚀失重测试、电化学试验与剥蚀后表面及深度方向腐蚀微观形貌观察,对三者的腐蚀形式和机理进行了分析。结果表明:母材腐蚀速率最大,自腐蚀电位最低,而腐蚀电流密度最大;两种接头焊缝/焊核的耐蚀性总体接近,都优于母材的,FSW焊核的耐蚀性最优。合金母材的腐蚀形式为层状剥蚀,TIG焊缝为晶间腐蚀,深度较小,FSW焊核为点蚀。三者的腐蚀均与析出相有关,母材的析出相粗大,与基体之间的电偶效应最明显;TIG焊缝析出相沿枝晶晶界排列,但析出相尺寸小,电偶作用弱于母材;FSW焊核析出相尺寸由于机械搅拌而变小且分布弥散,腐蚀性能有所改善。

The corrosion behavior of base metal of 2219 aluminum alloy and its friction stir-weld （FSW） joint and tungsten inert gas （TIG） joint was investigated by exfoliation corrosion test and potentiodynamic polarization curve test. The corrosion patterns and mechanism of above three materials were analyzed by making comparisons of corrosion mass loss, electrochemical corrosion property and micro-morphology of surface and cross-section after corrosion. The results show that the base metal had the largest corrosion rate, the lowest corrosion potential and the biggest corrosion current. The corrosion resistance of the weld or nugget of two joints was almost the same, and better than that of the base metal. The nugget of FSW joint was the best one. According to the classification of corrosion patterns, the base metal was exfoliation corrosion, the weld of TIG joint showed intergranular corrosion, and the nugget of FSW joint was pitting corrosion. The corrosion of the base metal and the welding joints was related with precipitated phase. The larger the size of precipitated phase was, the more obvious the galvanic effect was. The precipitated phase of the weld of TIG joint was along the dendritic boundary and showed the lower galvanic effect than the base metal due to its smaller size; on the contrary, the nugget of FSW joint had an improved performance of corrosion as a result of mechanical stirring which made the precipitated phase smaller and distributed uniformly.