Effects of Ce and Y on Modification and Corrosion Behavior of Mg-0.8%Si Alloy: A Correlation Study

Rare-earth (RE) elements (Ce and Y) addition on modification effect and corrosion behavior of the Mg-0.8%Si alloy were investigated in the present work. Their correlation was also discussed. The results indicated that both Ce and Y could effectively modify the eutectic Mg₂Si phase in the Mg-0.8%Si alloy. The coarse Chinese script type eutectic Mg₂Si phase was refined to rod or punctiform shape. The modification effect of Y was better than that of Ce. Si-RE-rich phases were formed in the RE-modified Mg-0.8%Si alloy. Both Ce and Y elements could improve the corrosion resistance. Y showed better effect than Ce. “Barrier effect” and “passive cathodic effect” were the main reasons for the improvement of corrosion resistance. After being modified by 0.5%Y, the corrosion rate in immersion test and the corrosion current density of the Mg-0.8%Si alloy decreased from 6.68 mg/cm²·h to 0.44 mg/cm²·h and from 145.1 μA/cm² to 33.8 μA/cm², respectively. Good modification effect exhibited good corrosion resistance due to the barrier effect of the film formed by Mg₂Si phases and corrosion products.