Microstructure and Corrosion Properties of Duplex-Structured Extruded Mg-6Li-4Zn-xMn Alloys

The extruded Mg-6Li-4Zn-xMn (x = 0, 0.4, 0.8, 1.2 wt%) alloys were prepared, and the microstructure of the test alloys was investigated by optical microscopy, scanning electron microscopy and transmission electron microscopy. The corrosion properties were determined by electrochemical measurements and immersion measurements in 3.5% NaCl solution. The results indicate that the extruded Mg-6Li-4Zn-xMn alloys are mainly composed of α-Mg phase, β-Li phase, Mn precipitates and some intermetallic compounds (MgLi2Zn). With the addition of Mn, stable corrosion products were formed on the surface of the test alloy, which can effectively inhibit further corrosion progress and improve the corrosion resistance. Mg-6Li-4Zn-1.2Mn alloy exhibits the best corrosion resistance, attributed to grain refinement, the improvement of the stability of corrosion product film and uniform distribution of fine second phases.