The Effect of Extrusion Ratio on the Corrosion Resistance of Ultrafine-Grained Mg-4Li-3Al-Zn Alloy Deformed Using Extrusion with a Forward-Backward Oscillating Die

In this study, the microstructure-dependent corrosion of fine-grained Mg-4Li-3Al-Zn alloys in the chloride containing solutions is described. The materials were processed using extrusion with a forward-backward oscillating die. The Mg-4Li-3Al-Zn alloys were extruded from o40 to o4 mm (R-1= 10:1, lambda(1) = 100), and also from o40 to o1 mm (R-2= 40:1, lambda(2) = 1600); the resulting microstructures were then analyzed. The results show that the corrosion of both alloys is strongly dependent on the processing parameters (mainly extrusion ratio), which in turn have a significant influence on the recrystallization stage. Interestingly, the higher the extrusion ratio, the lower the corrosion resistance of the alloy. The decreasing corrosion resistance of the alloy deformed at a higher extrusion ratio is related to the grain growth resulting from the more intense recrystallization processes that occurred during KoBo extrusion.