(中南大学 材料科学与工程学院，长沙 410083)
摘 要: 采用拉伸性能测试、慢应变速率拉伸测试、DSC分析、电导率测试及透射电镜观察，研究不同回归再时效(RRA)处理制度对7A55铝合金淬火预拉伸(W51)板材显微组织、拉伸性能和抗应力腐蚀(SCC)性能的影响。结果表明：采用120 ℃、24 h预时效，180 ℃、60 min回归处理和120 ℃、24 h终时效的RRA工艺，可使7A55合金获得与T6态相当的强度，而电导率大大提高，抗应力腐蚀性能接近T73态水平。7A55合金经适当的RRA处理后，晶内保持类似于T6状态的显微组织结构，为细小、弥散的η′相和极少量的η相；同时使晶界析出物的大小和分布特征与T73状态类似，为呈断续、孤立分布的粗化平衡相。
关键字: 7A55铝合金；回归处理；再时效处理；应力腐蚀；微观组织
（School of Materials Science and Engineering, Central South University, Changsha 410083, China）
Abstract:The effects of retrogression and reaging (RRA) treatment on the microstructure, tensile properties and resistance to SCC of a pre-stretched 7A55 aluminum alloy plate were studied by tensile test, slow strain rate tensile test, DSC analysis, conductivity measurement and transmission electron microscopy(TEM) observations. The results show that perfect mechanical and stress corrosion resistance properties can be obtained if the alloy is treated by the RRA of 120 ℃, 24 h pre-ageing, 180 ℃, 45 min retrogression and 120 ℃, 24 h re-aging. The strength of the alloy is almost the same compared with the T6 sample, while the conductivity increases greatly, and the stress corrosion resistance property enhances to the levels of T73 condition. Treated by proper RRA, small amount of η and a great mount of fine and dispersive precipitates η′ are observed in the matrix which is similar to that of T6 condition, while the coarse and discontinuous equilibrium precipitates are observed at the grain boundaries which is analogous to that of the T73 condition.
Key words: 7A55 Al alloy; retrogression treatment; reaging treatment; stress corrosion; microstructure
