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为了了解Pb-Mg-Al合金腐蚀的物理本质,本文采用基于第一性原理的赝势平面波方法系统地计算了Pb-Mg-Al合金中各物相的结合能、费米能级和局域态密度等电子结构参数,分析了合金的电化学腐蚀机理.计算结果表明:Pb-Mg-Al合金中各主要组成物相稳定性大小关系为Mg_(17)Al_(12)>Mg_2Pb>Mg;Mg,Mg_2Pb和Mg_(17)Al_(12)的费米能级存在E_f(Mg)>E_f(Mg_2Pb)>E_f(Mg_(17)Al_(12))的关系,说明Mg最容易失去电子,Mg_2Pb次之,Mg_(17)Al_(12)最难;局域态密度表明,在同样的外界条件下,体系中Mg相和Mg_2Pb相对于Mg_(17)Al_(12)均处于不稳定的状态,容易失去电子,即容易发生腐蚀.Pb-Mg-Al合金体系中不同物相的费米能级差构成了电化学腐蚀的电动势,导致电子从费米能级高的Mg相和Mg_2Pb相流向费米能级低的Mg_(17)Al_(12)相,使Pb-Mg-Al合金发生腐蚀.
In order to understand the physical nature of Pb-Mg-Al alloy corrosion, this paper systematically calculated the binding energy, the Fermi level and the local area of Pb-Mg-Al alloy by the pseudopotential plane wave method based on the first principle The results show that the phase stability of the major components in Pb-Mg-Al alloys is Mg 17 Al 12 Mg 2 Pb b Mg, The relationship between E_f (Mg)> E_f (Mg_2Pb)> E_f (Mg_ (17) Al_ (12)) exists in the Fermi level of Mg, Mg_2Pb and Mg_ (17) Al_ (12), which indicates that Mg is most likely to lose electrons and Mg_2Pb The second is that Mg_ (17) Al_ (12) is the hardest part for Mg_ (17) Al_ (12). The local density of states indicates that under the same external conditions, Mg and Mg_2Pb are all unstable with respect to Mg_ Easy to lose electrons, that is prone to corrosion.Pb-Mg-Al alloy system of different phases of the Fermi level differences constitute the electrochemical corrosion of the electromotive force, resulting in electrons from the Fermi level Mg phase and Mg_2Pb phase flow Fermi Mg_ (17) Al_ (12) phase with low energy level leads to corrosion of Pb-Mg-Al alloy.