Correlation between microstructure, tribology and corrosion behaviors of Mg-Al-Zn alloy via creating fine and uniform twins through submerged friction stir processing

Twins and fine microstructure can improve the surface properties of magnesium alloys. However, most of the current grain refinement and twinning technologies are costly or complex. In contrast, submerged friction stir processing (SFSP) is a cost-effective process. In this work, Mg-Al-Zn alloys with a fine and uniform twin structure were prepared by multi-pass SFSP with flowing water as coolant. The macro/micro-structure and properties of the surface layer under different processing conditions were characterized. The correlation between microstructure, tribology and corrosion behaviors was systematically studied. The results display that SFSP led to finer grains and created a large number of ultra-fine tensile twins and high-density dislocations in the processed zones compared with air-cooled FSP (AFSP). This unique microstructure resulted in synergistic enhancement of wear and corrosion resistance of Mg-Al-Zn alloy at room temperature.