顯微組織的非均勻性對AA2099-T8鋁鋰合金局部腐蝕的影響Effect of microstructural heterogeneity on localized corrosion of AA2099-T8 aluminum-lithium alloy

采用化學(xué)浸泡和動電位極化法，結(jié)合掃描電子顯微技術(shù)研究AA2099-T8鋁鋰合金的顯微組織對其局部腐蝕行為的影響。結(jié)果表明：合金的顯微組織不均勻，部分晶粒內(nèi)部存在高密度位錯或滑移帶組織；在3.5%NaCl(質(zhì)量分?jǐn)?shù))溶液中，粗大第二相顆粒與鋁基體間形成的腐蝕微電池引發(fā)輕微點蝕，其腐蝕行為與第二相顆粒的種類密切相關(guān)；嚴(yán)重局部腐蝕(SLC)與合金的擇優(yōu)形變及時效析出相有關(guān)。非均勻塑性變形使合金局部區(qū)域位錯密度升高，促進時效過程中活性T₁(Al₂CuLi)相在局部優(yōu)先析出，增大了該區(qū)域的腐蝕傾向，引發(fā)嚴(yán)重的局部腐蝕。

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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