Microstructure Evolution and Corrosion Performance of AZ31 Magnesium Alloy Sheets

AZ31 Mg alloy sheets were pre-stretched (PRS) at the angles of 0 degrees, 30 degrees, 45 degrees, 60 degrees and 90 degrees between the tensile direction and the extrusion direction at room temperature. Twinning was thus introduced and gradually increased. The microstructure evolutions and corrosion behavior were examined and compared. Results show that the corrosion performance of the twinned Mg alloy sheets is sensitive to the area fraction of twins. Meanwhile, the sheet possessing most area fraction of twins (similar to 52%) exhibits the best corrosion resistance. This is attributed to the subdivision of grains by introducing extension twin boundaries. Twinning brings about more grain boundaries that act as a corrosion barrier and thus improve the corrosion resistance.