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

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.