Effect of Microalloyed Al on Microstructure and Corrosion Behaviors of As-Cast Mg-Zn-Y-Mn Alloys

The effect of Al microalloying on microstructure and corrosion behaviors of as-cast Mg-6Zn-8.16Y-2.02Mn is investigated. Microstructural characterization reveals that Al addition can refine grain and lead to the formation of Al(Y, Zn) phase. When a 0.3 wt% Al is added, the alloy exhibits the lowest weight loss rate of 0.99 mm/Y and displays relatively uniform corrosion morphology. However, alloys with more Al addition present localized corrosion on the surface. It results from more W phase (Mg3Zn3Y2) and a little long-period stacking order (LPSO) phase along the grain boundary. Electrochemical tests are also used to rationalize the corrosion behaviors observed in weight loss. In conclusion, the decrease in corrosion rate is due to grain refinement, optimal quantification of Al(Y, Zn) with short-rod shape and LPSO phase.

Automated summary

The addition of Al in Mg-6Zn-8.16Y-2.02Mn alloy can refine grain and affect corrosion behaviors. A small amount of Al reduces weight loss rate and results in uniform corrosion morphology, while excessive Al addition leads to localized corrosion due to the presence of more W phase and LPSO phase.