Improved Discharge Performance of AZ72-0.05La Alloy Anode via Refining Mg17Al12 Phase

The morphology of phases in magnesium alloys is vitally important for their performance. It is found that improved discharge performance is achieved in AZ72-0.05La alloy via a refining Mg17Al12 phase by means of hot rolling. Before rolling, as-cast AZ72-0.05La alloy has a relatively coarse and strip-like Mg17Al12 phase. After rolling, the Mg17Al12 phase becomes much finer, showing a granulated shape. Due to the refinement of the Mg17Al12 phase, the discharge voltage and energy density of an Mg-air battery with as-rolled AZ72-0.05La alloy as the anode increases by 6% and 3% under a discharge current density of 20 mA·cm−2 in a 3.5% NaCl solution, respectively. The corrosion rate of the as-rolled AZ72-0.05La alloy is slightly larger than the as-cast AZ72-0.05La alloy, but still much lower than as-cast AZ72 alloy. The as-rolled AZ72-0.05La alloy possesses a discharge voltage of 0.74 V and an energy density of 918 mWh·g−1 under a discharge current density of 20 mA·cm−2, and a relatively low corrosion rate of 0.51 mg·cm−2·h−1, demonstrating good overall discharge performance. This work provides a method for improving the discharge performance of Mg-air batteries.