铝合金表面电偶腐蚀与电子功函数的关系

铝合金中经常会引入一些第二相来改善其性能,第二相由于和铝基体的电位差不同,将会对铝合金的局部腐蚀产生重大的影响.为了揭示铝合金腐蚀的物理本质,本文利用基于密度泛函理论第一性原理的计算方法,详细计算了铝合金中一些主要第二相(Al_2Cu、Al_3Ti和Al_7Cu_2Fe)的多种晶面的电子功函数,分析了电子从各个晶面逸出的难易,求得了第二相与Al基体的本征电势差,我们发现不同的晶面暴露在合金最外层,会显著地影响本征电势差;即便是同一晶面,暴露在最外层的原子种类和构型不同,对腐蚀的影响也不一样.从电子的层面解释了电偶腐蚀发生的原因.

Correlation between Galvanic Corrosion and Electronic Work Function of Al Alloy Surfaces

Al alloys contain some secondary phases to improve their properties. These secondary phases have different potentials to the Al matrix, which greatly affect the localized corrosion of Al alloys. In order to reveal the physical nature of Al alloy corrosion, we use the first-principles method based upon density functional theory to calculate the work function of the main secondary phases (Al₂Cu, Al₃Ti, and Al₇Cu₂Fe). The difficulty of electrons escaping from various crystal planes was analyzed, and the potential difference between the secondary phases and Al matrix was obtained. We find that different crystal planes exposed to the outmost layer significantly impacted on the potential difference. Different atomic types at the outmost layer play different roles in Al alloy corrosion, even for the same crystal surface. The causes of galvanic corrosion were thus revealed.