Mg_(2)Sn对镁合金耐腐蚀性能影响的计算分析与验证

Calculation Analysis and Verification of the Effect of Mg_(2)Sn on Corrosion Resistance of Magnesium Alloy

目的 从计算角度分析镁合金中的主要析出相Mg_(2)Sn对ZA系镁合金耐蚀性能的影响,并采用试验测试的方法对其进行验证。方法 利用第一性原理计算方法对Mg_(2)Sn的表面能与功函数进行计算,通过与构建的Mg基体以及Zn、Al掺杂的Mg表面的表面能、功函数进行对比分析,分析Mg_(2)Sn对ZA系镁合金耐蚀性能的影响。为了验证计算结果,制备Mg-5Zn-3Al-0Sn合金以及Mg-5Zn-3Al-3Sn合金,通过电化学实验对2种合金的耐蚀性能进行对比分析,研究Mg_(2)Sn对ZA系镁合金耐蚀性能的影响。结果 计算了Mg基体表面能与功函数,与其他成果计算结果的符合程度较好。对Mg_(2)Sn不同表面的功函数进行计算,通过与Mg、Mg-Zn、Mg-Al表面的计算结果进行对比,发现Mg_(2)Sn的功函数均要更高。XRD测试结果表明,制备的Mg-5Zn-3Al-3Sn合金中有明显的Mg_(2)Sn相。电化学测试结果表明,Mg-5Zn-3Al-0Sn的耐蚀性能要好于Mg-5Zn-3Al-3Sn的耐蚀性能。结论 通过第一性原理计算发现,Mg_(2)Sn的功函数高于Mg基体表面的功函数,说明在合金中易发生微电偶腐蚀,Mg_(2)Sn充当阴极相促进Mg基体的腐蚀。电化学测试结果说明,当合金中存在明显的Mg_(2)Sn相时,合金的耐蚀性能降低,腐蚀电位达到-1.21 V。

The work aims to analyze the effect of the main precipitate Mg_(2)Sn of magnesium alloy on the corrosion resistance of ZA series magnesium alloy from the perspective of calculation and carry out verification by test. The first-principles calculation method was used to calculate the surface energy and work function of Mg_(2)Sn. The effect of Mg_(2)Sn on the corrosion resistance of ZA series magnesium alloy was analyzed by comparing the surface energy and work function of the constructed Mg matrix and the Mg doped with Zn and Al. In order to verify the calculation results, Mg-5Zn-3Al-0Sn alloy and Mg-5Zn-3Al-3Sn alloy were prepared. The corrosion resistance of the two alloys was compared through electrochemical experiment, and the effect of Mg_(2)Sn on the corrosion resistance of ZA series magnesium alloy was studied. The surface energy and work function of Mg matrix were calculated, which were in good agreement with other results. The work functions on different surfaces of Mg_(2)Sn were calculated. By comparing the results on surfaces of Mg, Mg-Zn and Mg-Al, it was found that the work functions on the surfaces of Mg_(2)Sn were higher. XRD results indicated that the Mg-5Zn-3Al-3Sn alloy had obvious Mg_(2)Sn phase. The electrochemical test results showed that the corrosion resistance of Mg-5Zn-3Al-0Sn was better than that of Mg-5Zn-3Al-3Sn. According to the first-principles calculation, the work function of Mg_(2)Sn is higher than that of Mg matrix surface, indicating that micro galvanic corrosion is easy to occur in the alloy, and Mg_(2)Sn acts as a cathode phase to promote the corrosion of Mg alloy. The results of electrochemical test also show that the corrosion resistance of the Mg alloy decreases when there is obvious Mg_(2)Sn phase, and the corrosion potential reaches ‒1.21 V.