Effect of preaging temperature on microstructure evolution, mechanical and corrosion behavior of RRA‐treated high‐zinc 7068 alloy

Materials and Corrosion Pub Date : 2022-05-03 DOI:10.1002/maco.202213196

Ankur Kumar, G. Chaudhari, S. Nath

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引用次数: 2

Abstract

Mechanical and corrosion behavior of high‐strength, high‐zinc (>7 wt%) containing 7068 aluminum alloy is investigated after employing different retrogression and reaging (RRA) treatments. The effect of preaging conditions on the distribution of copper, zinc, and magnesium, the volume fraction of η′ phase, and the width of precipitate free zones (PFZ) have been investigated. Microstructural and compositional features characterized by scanning electron microscope‐energy dispersive spectroscopy, scanning transmission electron microscope, and differential scanning calorimetry are correlated with hardness and corrosion performance. The localized attack is manifested in the dissolution of second phase precipitates which occurs from selective leaching of magnesium and aluminum. A combination of two opposite effects, that is, the presence of nobler, high‐copper grain boundary precipitates and microgalvanic effect of PFZ along with the distribution of alloying elements, that is, Cu, Zn, and Mg govern the electrochemical behavior of RRA‐treated 7068 alloy. Optimum preaging and RRA conditions are identified for this high‐zinc 7xxx series alloy.

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预温对RRA处理高锌7068合金组织演变、力学和腐蚀行为的影响

研究了高强度、高锌(bbb707 wt%)含7068铝合金在不同的时效(RRA)处理后的力学和腐蚀行为。研究了预浸条件对铜、锌、镁分布、η′相体积分数和无析出区宽度的影响。通过扫描电镜-能量色散光谱、扫描透射电镜和差示扫描量热法表征的显微组织和成分特征与硬度和腐蚀性能相关。局部侵蚀表现为镁铝选择性浸出过程中第二相析出物的溶解。两种相反的作用，即更高贵的高铜晶界析出物的存在和PFZ的微电效应以及合金元素(Cu、Zn和Mg)的分布，共同决定了RRA处理7068合金的电化学行为。确定了高锌7xxx系列合金的最佳预时效和RRA条件。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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Materials and Corrosion

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