摘要:
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.
Abstract:
The cohesive energies,Fermi energies and local density of states（LDOS） are calculated by the first-principles based on pseu- dopotential plane wave method in this paper to investigate the physical nature of corrosion of Pb-Mg-Al alloy.The mechanism of electrochemical corrosion is analyzed according to the calculated electronic structure parameters.The results show that the stable phase in Pb-Mg-Al alloy is Mg_（17）Al_（12）Mg_2PbMg.The Fermi energy（E_f） values of these phases with E_f（Mg）E_f（Mg_2Pb）E_f （Mg_（17）Al_（12）） indicate that Mg is most likely to lose electrons while Mg_（17）Al_（12） is difficult.LDOS result reveals that Mg and Mg_2Pb phases are unstable compared with Mg_（17）Al_（12） in the same external conditions,they are more likely to lose electrons and easier to corrod. The difference in Fermi energy between different phases in Pb-Mg-Al alloy forms the electrodynamic force of the electrochemical corrosion,which leads electrons to flow from the Mg and Mg_2Pb phases with higher Fermi energy to Mg_（17）Al_（12） phase with lower Fermi energy,further to corrode in Pb-Mg-Al alloy.
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