热机械加工对 AA2099铝锂合金局部腐蚀敏感性及其扩展机理的影响

摘要

In order to manifest the influence of specific microstructural component on the development of severe localized corrosion in an AA2099 aluminum−lithium alloy, the corrosion behavior of the alloy subjected to solution heat treatment, cold working and artificial ageing was investigated. Immersion testing and potentiodynamic polarization were employed to introduce localized corrosion; scanning electron microscopy and transmission electron microscopy were used to characterize the alloy microstructure and corrosion morphology. It was found that the susceptibility of the alloy to severe localized corrosion was sensitive to thermomechanical treatments. Additionally, the state of alloying elements influenced the mechanism of localized corrosion propagation. Specifically, the alloy in T8 conditions showed higher susceptibility to severe localized corrosion than that in other conditions. During potentiodynamic polarization, the alloy in solution heat-treated and T3 conditions displayed crystallographic corrosion morphology while the alloy in T6 and T8 conditions exhibited selective attack of grain interiors and grain boundaries in local regions.%为了突出特定显微组织组成对 AA2099铝锂合金严重局部腐蚀的影响，对比研究了固溶、预冷变形及人工时效状态下 AA2099合金的腐蚀行为。通过浸泡和动电位极化在合金表面引入局部腐蚀；采用扫描电子显微镜和透射电子显微镜表征合金的显微组织和腐蚀形貌。研究表明：该合金的严重局部腐蚀敏感性与其热机械加工过程密切相关，且合金元素的存在方式影响腐蚀的扩展机理。T8状态合金的严重局部腐蚀敏感性比其他状态合金更高；当进行动电位极化时，固溶和 T3状态合金表现为晶体学腐蚀特征而 T6和 T8状态合金表现为局部区域晶粒和晶界的择优腐蚀。