Effect of Sr on Microstructure and Corrosion Resistance of AZ31B Magnesium Alloy

The effect of strontium on microstructure and corrosion resistance of magnesium alloy was studied. When the addition of Sr was more than 0.3%, the amount of Mg17Al12 phase in the alloy decreased, and distribution became more uniform, reticular Al4Sr at grain boundaries formed and microstructure of the alloy was also refined obviously. The corrosion rate of AZ31 alloy with an addition of 0.9% Sr decreased to 50%. This was mainly caused by the formation of reticular Al4Sr phase, which acted as an effective barrier against corrosion and made the corrosion potential increased and the corrosion current density decreased. But when the Sr addition was more than 1.2%, eutectic structure distributed along with grain boundaries to form discontinued net-like structure and the grain size increased again.