(1. 中南大学 材料科学与工程学院，长沙 410083；
2. 广西南铝加工有限公司 广西铝合金材料与加工重点实验室，南宁 530031；
3. 中南大学 有色金属材料科学与工程教育部重点实验室，长沙 410083)
摘 要: 本文研究了一种7XXX系铝合金厚板T6I76、T73和T6三种时效状态的硬度、室温拉伸和电导率，并采用晶间腐蚀、剥落腐蚀、极化曲线和交流阻抗测试方法研究了其局部耐腐蚀性能。结果表明：T6I76试样的强度和硬度与T6试样的相当，但局部耐腐蚀性能明显增强，且优于T6试样和T73试样的。T6I76试样经过预时效、淬火和低温长时间时效处理后，晶内沉淀强化相(η′相)特征与T6试样相似，但强度更大；与T73试样相比，T6I76试样的η相中Cu含量更高、Zn含量更低、间距更大，且晶界附近无沉淀析出带宽度更窄，这能有效地阻断沿晶阳极溶解通道，得到更好的局部耐腐蚀性能。
关键字: 7XXX系铝合金；断续时效；力学性能；晶间腐蚀；剥落腐蚀
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Guangxi Key Laboratory of Materials and Processes of Aluminum Alloys, ALG Aluminium Inc, Nanning 530031, China;
3. Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083, China）
Abstract:The hardness, room temperature tensile properties and electrical conductivity of a 7XXX series aluminum alloy plate in T6I76, T73 and T6 under three aging conditions were studied and the local corrosion properties of the alloy were investigated by means of intergranular corrosion tests, exfoliation corrosion tests, polarization curve and electrical impedance tests. The results show that the strength and hardness of the T6I76 sample are equivalent to those of the T6 sample, but the local corrosion resistance is significantly better than that of the T6 and T73 sample. The microstructure results of scanning transmission electron microscopy (SEM) and high-angle annular dark-field transmission electron microscopy (HAADF-TEM) show that, due to the extended pre-ageing time at relatively low temperatures, the fine and dense age-hardening η′ precipitates seemed to be identical for both T6I76 sample and T6 sample. The results have also shown that the grain boundary η phase in T6I76 temper has a higher Cu content, a lower Zn content than that in T73 temper. The width of the precipitation free zone (PFZ) near the grain boundary is narrower after interrupt ageing treatment, which can effectively block the anode dissolution, therefore a better local corrosion performance is obtained.
Key words: aluminium 7XXX alloy; interrupt aging; mechanical properties; intergranular corrosion; exfoliation corrosion
