不同热处理工艺对Al-3.8Zn-1.6Mg铝合金微结构与腐蚀行为作用的探讨

黄磊萍¹，杨修波^2*，陈江华¹，章国辉¹，赵新奇¹

（湖南大学 1. 材料科学与工程学院高分辨电镜中心；2. 物理与微电子科学学院应用物理系；湖南 长沙410082）

摘  要  本文针对一种经历了三级时效后获得优良力学性能的7N01铝合金，采用慢应变速率拉伸、剥落腐蚀测试，并采用透射电镜系统研究了该合金局部腐蚀行为与微观结构的关系。结果表明，三级时效状态的7N01铝合金，相比直接热处理（T4、T5、T6）的材料，其抗应力腐蚀性能和抗剥落腐蚀性能均可获得显著提高。透射电镜观察发现：T4状态合金中晶界析出相以细小的GP区以及溶质原子团簇为主，且晶界处元素分布均匀；T5状态合金中晶界析出相粗大，存在晶界无析出带（PFZ），Zn、Mg元素于晶界析出相处富集；T6状态合金中晶界析出相细小且接近连续分布，Zn、Mg元素于晶界析出相处富集；虽然三级时效工艺后Zn、Mg元素也于晶界析出相处富集，但晶界析出相粗大且断续程度加大，形成较宽的耐腐蚀的PFZ，因此有着更好的抗腐蚀性能。

关键词  7N01铝合金；时效；析出相；腐蚀

中图分类号：TG146.21；TG115.21⁺5.3    文献标识码：A    doi:10.3969/j.issn.1000-6281.2017.03.005

Influence of different aging process on microstructure and corrosion behavior of Al-3.8Zn-1.6Mg aluminum alloy

HUANG Lei-ping¹，YANG Xiu-bo^2，*，CHEN Jiang-hua¹，ZHANG Guo-hui¹，ZHAO Xin-qi¹

(1. Center for High Resolution Electron Microscopy, College of Material Science and Engineering, Hunan University；2. Department of Applied Physics, School of Physics and Electronics, Hunan University, Changsha Hunan 410082, China)

Abstract  Influence of a three-step-ageing treatment on the EXCO (exfoliation corrosion) and stress corrosion cracking (SCC) resistance of Al-3.8Zn-1.6Mg aluminum alloy was investigated by the slow strain rate technique (SSRT) and EXCO test, which used TEM, EDS and SEM. It was shown that the three-step-aged alloy had better EXCO and SCC resistance, compared with the directly one-step-aged alloy. Transmission electron microscopy (TEM) showed that the grain boundary precipitates in the T4 state alloy were mainly composed of small Guinier-Preston (GP) zone and solute-atom-clusters, and the elements in the grain boundary were uniformly distributed. The T5 state alloy had coarse grain boundary precipitates (GBP) and precipitated in the free zone (PFZ), Zn and Mg were enriched in the GBP; T6 state alloy had fine GBP, and Zn and Mg elements were enriched in the GBP. While the three-step-aged alloy could improve corrosion resistance because of the more discrete and coarser GBP and wider PFZ.

Keywords  7N01 alloy; ageing; precipitate; corrosion

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