显微组织的非均匀性对AA2099-T8铝锂合金局部腐蚀的影响Effect of microstructural heterogeneity on localized corrosion of AA2099-T8 aluminum-lithium alloy

采用化学浸泡和动电位极化法，结合扫描电子显微技术研究AA2099-T8铝锂合金的显微组织对其局部腐蚀行为的影响。结果表明：合金的显微组织不均匀，部分晶粒内部存在高密度位错或滑移带组织；在3.5%NaCl(质量分数)溶液中，粗大第二相颗粒与铝基体间形成的腐蚀微电池引发轻微点蚀，其腐蚀行为与第二相颗粒的种类密切相关；严重局部腐蚀(SLC)与合金的择优形变及时效析出相有关。非均匀塑性变形使合金局部区域位错密度升高，促进时效过程中活性T₁(Al₂CuLi)相在局部优先析出，增大了该区域的腐蚀倾向，引发严重的局部腐蚀。

The influence of microstructure on localized corrosion of the AA2099-T8 aluminum-lithium alloy was investigated using electrochemistry and scanning electron microscopy. The result shows that the microstructure of the alloy is not uniform and high densities of dislocations and slip bands are found within some of the grains. The micro-galvanic coupling between coarse second phase particles and aluminum matrix leads to mild pitting corrosion and the corrosion behavior is related to the types of the phase particles. Severe localized corrosion (SLC) is associated with heterogeneous plastic deformation and preferential precipitation during aging. Heterogeneous plastic deformation induces that population density of dislocations increases and number or volume fraction of the electrochemically active T₁(Al₂CuLi) phase consequently increases after artificial aging, resulting in increased corrosion susceptibility in local regions which leads to SLC.

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