(1. 常州大学 材料科学与工程学院，常州 213164；
2. 常州大学 江苏省材料表面科学与技术重点实验室，常州 213164；
3. 中南大学 材料科学与工程学院，长沙 410083)
摘 要: 采用维氏硬度计和加速腐蚀试验，分别测试Al-1.1Mg-1.2Si-0.9Cu合金(质量分数，%)在220 ℃时效过程中硬化行为和IGC敏感性。结果表明：合金在过时效阶段能够发生IGC→PC→IGC的腐蚀行为转变，出现所谓的PC→IGC再敏化现象。过时效阶段晶界Q相出现连续→断续→连续的分布特征变化，决定其与无析出区能否构成连续腐蚀微电池，是合金发生IGC→PC→IGC转变的主要原因。利用晶界析出相粗化与长大过程同步进行、先后主导的观点能够合理地解释晶界Q相分布特征和无析出区宽度在过时效阶段的变化规律。
关键字: Al-Mg-Si-Cu合金；过时效；析出；晶间腐蚀；坑蚀
（1. School of Materials Science and Engineering, Changzhou University, Changzhou 213164, China;
2. Jiangsu Key Laboratory of Materials Surface Science and Technology, Changzhou University, Changzhou, 213164, China;
3. School of Materials Science and Engineering, Central South University, Changsha, 10083, China）
Abstract:Based on the Vickers hardness measurement and acceleration corrosion test, the hardening behavior and IGC susceptibility of an Al-1.1Mg-1.2Si-0.9Cu alloy (mass fraction, %) aged at 220 ℃ were investigated. The results show that the corrosion behaviors change in the sequence of IGC→PC→IGC during over-ageing of the peak-aged alloy, which verifies the re-sensitization to IGC. The transmission electron microscopy observation results indicate that the continuous→discontinuous→continuous distribution of grain boundary Q phase precipitates determines whether the continuous electrochemical microcouples can form along the grain boundaries, which is responsible for the transition of IGC→PC→IGC further. Furthermore, a mode of synchronous development and successive domination for coarsening and growth is proposed to explain reasonably the distribution of grain boundary Q phase precipitates and width of precipitate free zones during over-ageing.
Key words: Al-Mg-Si-Cu alloys; over-ageing; precipitation; intergranular corrosion; pitting corrosion
