The corrosion resistance and discharge performance of as-extruded AZ91 alloy synergistically improved by the addition of submicron SiCp

Abstract

In order to reveal the influence of submicron SiCp on the corrosion and discharge behaviors of extruded AZ91 alloy, the extruded AZ91 alloy and 0.5 μm SiCp (0.5 vol.%)/AZ91 composite were subjected to immersion, electrochemical, and Mg-air battery tests. The results show that the introduction of submicron SiCp not only reduces the weightless corrosion rate of the extruded AZ91 alloy from 3.09 mm/y to 2.18 mm/y, but also increases its discharge voltage and stability at current densities ranging from 2.5 mA cm−2 to 40 mA cm−2. The improvement of corrosion resistance and discharge activity are attributed to the refined grains and precipitates, as well as the weakened basal texture owing to the addition of the minor submicron SiCp. Extruded AZ91 alloy has a coarse and unevenly distributed Mg17Al12 phase and strong basal texture. The coarse phase and more grains with basal texture as cathode lead to the local corrosion of magnesium in the corrosion process and the local dissolution of magnesium in the discharge process. After adding 0.5 vol.% submicron SiCp, the Mg17Al12 phase is fined and evenly distributed, and the basal texture is weakened, which not only weakens the galvanic corrosion but also promotes the uniform corrosion of magnesium. As a result, the corrosion resistance is improved. In addition, the discharge activity benefits from refined grains and the easily dissolving discharge product resulting from uniform dissolution of magnesium. This work provides new ideas for achieving the synergistic improvement of corrosion resistance and discharge performance of magnesium alloy.