Microstructure and corrosion resistance of a duplex structured Mg-7.5Li-3Al-1Zn

This study describes the corrosion resistance of extruded, and extruded with post-processing annealing, Mg-7.5Li-3Al-1Zn alloys. The results demonstrate that extrusion at 350 degrees C with an extrusion speed 0.5 s(-1) does not lead to the full recrystallization of the alloy, and the material still exhibits a dendritic microstructure. The post-processing annealing triggers the microstructure transformation, and the relative composition of the alloy changes. The ratio of beta(Li) to alpha(Mg) in the extruded alloy was 29-71%; after annealing amount of beta(Li) increased, and the ratio of beta(Li) to alpha(Mg) in the annealed alloy was 35-65%. Corrosion testing shows that in 3.5 wt% NaCl the extruded alloys immediately undergo strong dissolution. As a result of the subsequent annealing, an improvement of corrosion resistance is observed. The higher amount of beta(Li) in the annealed alloy reduces the area ratio of cathodic to anodic sites of corrosion, and this makes the annealed alloy more resistive under the analyzed conditions. (C) 2020 Chongqing University. Publishing services provided by Elsevier B.V. on behalf of KeAi Communications Co. Ltd.

Automated summary

The study found that the relative composition of Mg-7.5Li-3Al-1Zn alloy changed after extrusion and post-processing annealing, with an increase in beta(Li) content leading to improved corrosion resistance.