Corrosion behavior of Mg-3Al-1Zn alloy with different grain refinement strategies

Although the influence of grain boundaries (GB) or twin boundaries (TB) on corrosion resistance has been studied, there is no comparative study addressing the corrosion behavior of the two types of grain refinement. In this work, a comparative study of the corrosion behavior of samples with coarse grains (GB-coarse), fine grains (GB-refined), twin boundaries (TB-refined), and twin boundaries with solute atoms (TBS-refined) has been made. Results indicate that grain boundary refinement is more effective than twin boundaries in improving the corrosion resistance when grains are refined to similar grain sizes. The GB-refined sample show a typical corrosion band along rolling direction, while the corrosion in TB-refined counterparts preferentially occurs in twins. Twin boundaries improve corrosion resistance exclusively at an early stage, while an increase in corrosion rate after immersion occurs at longer times. In addition, segregation of solute atoms at twin boundaries further contributes to improving corrosion resistance.