Y元素对均匀态Mg-6Zn-0.25Ca镁合金耐蚀性能的影响

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

摘要:

研究了Y元素对均匀态Mg-6Zn-0.25Ca合金耐蚀性能的影响。通过XRD、OM、SEM、失重、析氢和极化曲线实验研究了均匀态Mg-6Zn-0.25Ca和Mg-6Zn-1Y-0.25Ca这2种合金的微观组织及耐蚀性能。研究表明，均匀态Mg-6Zn-0.25Ca合金的第二相是Mg₂Ca，加入Y元素后平均晶粒尺寸稍有变大，Mg₂Ca相减少，还生成新的第二相Mg₁₂ZnY、Mg₃Y₂Zn₃，并且第二相体积分数增加且分布更加均匀，这使得在腐蚀试验中镁基体上形成更加致密的腐蚀膜，该腐蚀膜可以起到屏障作用，新生成的Mg₁₂ZnY、Mg₃Y₂Zn₃都分布在晶界附近或枝晶间，显著降低了合金在腐蚀液中的电化学活性。这些使得Mg-6Zn-0.25Ca合金在3.5wt% NaCl的溶液中氢气析出量减少，增加Y元素使Mg-6Zn-0.25Ca合金的自腐蚀电位提高，并且减小自腐蚀电流密度，即有效地增强了均匀态Mg-6Zn-0.25Ca合金的耐蚀性能。所以Mg-6Zn-1Y-0.25Ca合金的耐蚀性能远高于 Mg-6Zn-0.25Ca合金。

Abstract:

The effect of Y on the corrosion resistance of homogenized Mg-6Zn-0.25Ca was studied. The microstructure and corrosion behavior of the homogenized Mg-6Zn-0.25Ca and Mg-6Zn-1Y-0.25Ca alloys were characterized by XRD, OM, SEM, mass loss, hydrogen evolution and polarization curve experiments. The results show that the secondary phase of homogeneous Mg-6Zn-0.25Ca alloy is Mg₂Ca, and the average grain size increases slightly after the addition of Y element, while the Mg₂Ca phase decreases. New secondary phases Mg₁₂ZnY and Mg₃Y₂Zn₃ are also formed, and the volume fraction of them increases and the distribution is more uniform. This enables a denser and more compact corrosion film to form on the magnesium matrix during the corrosion test, which can act as a barrier. The Mg₁₂ZnY and Mg₃Y₂Zn₃ are distributed near the grain boundary or between the dendrites, which significantly reduces the electrochemical activity of the alloy in corrosive solution. Thus, the hydrogen precipitation of Mg-6Zn-0.25Ca alloy is reduced in 3.5wt% NaCl solution. By increasing the Y element, the self-corrosion potential of Mg-6Zn-0.25Ca alloy is increased and self-corrosion current density is reduced, thereby improving the corrosion resistance of homogeneous Mg-6Zn-0.25Ca alloys. Therefore, the corrosion resistance of Mg-6Zn-1Y-0.25Ca alloy is much higher than that of Mg-6Zn-0.25Ca alloy.