The intergranular corrosion (IGC) behavior of an extruded 6005A alloy profile with the coexisting of peripheral coarse grain (PCG) structure and partial recrystallized grain (PRG) structure was investigated by using an accelerated corrosion test, electrochemical impedance spectroscopy and a quasi in situ examination of IGC process. PCG structure was found to have a unique IGC behavior that pitting corrosion and subsequent IGC are less severe and will not be transformed into intragranular corrosion as they were found in PRG structure. Microstructure characterization reveals that the microstructural differences in grain boundary precipitates, primary α-AlFeMnSi intermetallic particles and grain characteristic between PCG structure and PRG structure are the reason for these phenomena. Further analysis indicates that the grain boundaries decorated with more AlFeMnSi particles and Q phase precipitates are more sensitive to corrosion, where Q phase precipitates are the primary cathodes and the most important factor affecting IGC; AlFeMnSi particles are supposed to initiate pitting corrosion since they are dissolved as anodes in the early stage of corrosion. With the development of corrosion, they are transformed into cathodes and become the bridges of IGC propagation by connecting the Q phase precipitates at grain boundary. In addition, grain characteristic was also found to have great effects on IGC. With the decrease in grain size and the increase in the frequency of high-angle grain boundaries and the dislocation density, corrosion becomes more severe and more likely to be transformed into intragranular corrosion.

中文翻译：

---

不同显微组织挤压6005A合金型材的晶间腐蚀行为

通过加速腐蚀试验、电化学阻抗谱和准原位检测，研究了外周粗晶 (PCG) 结构和部分再结晶 (PRG) 结构共存的挤压 6005A 合金型材的晶间腐蚀 (IGC) 行为IGC 流程。PCG 结构被发现具有独特的 IGC 行为，点腐蚀和随后的 IGC 不太严重，不会像在 PRG 结构中发现的那样转化为晶内腐蚀。显微组织表征表明，晶界析出物、初生 α-AlFeMnSi 金属间化合物颗粒的显微组织差异以及 PCG 结构和 PRG 结构之间的晶粒特征是这些现象的原因。进一步分析表明，装饰有更多AlFeMnSi颗粒和Q相沉淀物的晶界对腐蚀更敏感，其中Q相沉淀物是主要阴极，也是影响IGC的最重要因素；AlFeMnSi 颗粒被认为会引发点蚀，因为它们在腐蚀的早期阶段作为阳极溶解。随着腐蚀的发展，它们转变为阴极，通过连接晶界处的 Q 相沉淀物而成为 IGC 传播的桥梁。此外，还发现颗粒特性对 IGC 有很大影响。随着晶粒尺寸的减小和大角度晶界频率和位错密度的增加，腐蚀变得更加严重，更容易转化为晶内腐蚀。