(1. 东北轻合金有限责任公司，哈尔滨 150060；
2. 中南大学 材料科学与工程学院，长沙 410083)
摘 要: 采用透射电镜观察、剥落腐蚀实验以及慢应变速率拉伸实验研究时效处理制度对7A55合金预拉伸板材析出相特征、电导率和腐蚀性能的影响。结果表明：在T651峰时效态，7A55合金的晶内析出相主要为细小、弥散分布的GP区和η′相，晶界析出相呈连续分布，在T651状态合金虽然具有最高强度，但剥落腐蚀倾向严重，应力腐蚀敏感性最大；T7351时效态晶内析出相主要为短棒状的粗大η相，晶界析出物呈粗大、非连续分布，此时虽然耐腐蚀性能最好，但强度损失很大；T7651、T7451时效态晶内既存在与基体半共格的η′相，又存在与基体不共格的η相，晶界析出相比较粗大且析出相之间的间距增大，呈断续分布，因此，在T7651和T7451状态，合金强度损失不大，而耐蚀性得到明显改善。
关键字: 7A55合金；双级时效；微观组织；剥落腐蚀；应力腐蚀；电导率
corrosion behavior of 7A55 alloy plate
（1. Northeast Light Alloy Co., Ltd., Harbin 150060, China;
2. School of Materials Science and Engineering, Central South University, Changsha 410083, China）
Abstract:The effects of aging treatments on the microstructure, corrosion resistance and electrical conductivity of pre-stretched 7A55 alloy plate were investigated by transmission electron microscopy(TEM) and slow strain rate tension test. The results show that in T65l condition the main precipitates are GP zones and η′ phase in the matrix, and the grain boundary precipitates distribute continuously. In T651 condition the strength of 7A55 alloy plate is the highest; however the alloy has a serious tendency to exfoliation corrosion and very high sensitivity to stress corrosion crack. In T7351 condition the coarse rod-like η precipitates are mainly observed in the matrix and the grain boundary precipitates are coarse obviously and distribute sparsely. So, the corrosion resistance is the highest but the strength decreases to the lowest level. In T7651 and T7451 conditions, both η′ and η precipitates exist in the matrix, and the coarse and isolate precipitates present in the grain boundaries, which contributes to the improvement of the corrosion resistance and electrical conductivity, while the decrease of tensile strength is small.
Key words: 7A55 alloy plate; double aging; microstructure; exfoliation corrosion; stress corrosion; electrical conductivity
