Enhancement of corrosion resistance of a high Zn-yttrium aluminum alloy

Abstract The corrosion resistance of a high Zn (11 wt%) aluminum alloy was found to be significantly improved by 45% when doped with Y (solid solution limit 1.4 wt %), while the hardness of the material is only reduced by 3.5%. Although corrosion is frequently observed in the grain boundaries of high Zn aluminum alloys, it is not observed in the grain boundary of the Y-included alloys under current approach, in spite of the increased volume of grain boundary phases. The content of Mg and Zn decreased in the grain boundary precipitates as the Y content increases, leading to an increase of the corrosion potential of these grain boundary phases. The calculated atomic binding energies, diffusion energies and surface energies suggested that Y substitution has improved the binding forces between alloy elements Mg, Cu, Zn and Al, but has a different effect on Cr. The precipitates in grain boundaries appear to have converted from the Al-based solid solution into a more stable intermetallic compound of MgZn2-type.