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.