Sn元素对均匀态Mg-6Zn-0.25Ca镁合金耐腐蚀性能的影响

Effect of Sn Element on Corrosion Resistance of Homogeneous Mg-6Zn-0.25Ca Magnesium Alloy

摘要:

研究了添加1wt%的Sn对均匀态Mg-6Zn-0.25Ca合金耐腐蚀性能的影响。通过OM、XRD、SEM、析氢、失重以及极化曲线实验来分析Mg-6Zn-Sn-0.25Ca以及Mg-6Zn-0.25Ca 2种合金的耐腐蚀性能。结果表明，Mg-6Zn-0.25Ca合金主要第二相是Mg₂Ca相，再加入Sn元素后，Mg-6Zn-Sn-0.25Ca合金中第二相的主要存在方式为Mg₂Sn相、Mg₂Ca相和少量CaMgSn相。加入Sn元素后，合金第二相分布更加均匀；合金的平均晶粒尺寸由145.6 μm下降到了114.2 μm，因为高熔点的Mg₂Sn相可以作为α-Mg基体非自发结晶的异质形核核心，从而细化晶粒尺寸。在两者共同作用下，合金因腐蚀而产生的腐蚀产物氧化膜更加绵密，阻止了析氢反应的继续进行。此外，极化曲线表明，Mg-6Zn-0.25Ca合金的自腐蚀电位和自腐蚀电流密度分别为–1.729 V和2.106×10^–5 A/cm²，添加1wt% Sn元素后，自腐蚀电位升高到–1.525 V，自腐蚀电流密度减小为8.561×10^–6 A/cm²，增强了Mg-6Zn-Sn-0.25Ca合金的耐蚀能力。

Abstract:

The effect of adding 1wt% Sn on the corrosion resistance of homogeneous Mg-6Zn-0.25Ca alloy was studied. The corrosion resistance of Mg-6Zn-Sn-0.25Ca and Mg-6Zn-0.25Ca alloys was analyzed by OM, XRD, SEM, hydrogen evolution, mass loss and polarization curve experiments. The results show that the main secondary phase in Mg-6Zn-0.25Ca alloy is Mg₂Ca phase, and after Sn addition, the main existence form of the secondary phase in Mg-6Zn-Sn-0.25Ca alloy is Mg₂Sn phase, Mg₂Ca phase and a small amount of CaMgSn phase. After adding Sn, the secondary phase of the alloy is more evenly distributed and the average grain size of the alloy decreases from 145.6 μm to 114.2 μm, because the Mg₂Sn phase with high melting point can act as a heterogeneous nucleation core for non-spontaneous crystallization of the α-Mg matrix, thereby refining the grain size. Under their combined effect, the oxide film produced during alloy corrosion becomes denser, thereby preventing the hydrogen evolution reaction. In addition, the polarization curves show that the self-corrosion potential and self-corrosion current density of Mg-6Zn-0.25Ca alloy are –1.729 V and 2.106×10^-5 A/cm², respectively. After adding 1wt% Sn, the self-corrosion potential increases to –1.525 V, while the self-corrosion current density decreases to 8.561×10^-6 A/cm², which enhances the corrosion resistance of Mg-6Zn-Sn-0.25Ca alloy.