Effect of Al–Ti–B master alloy on microstructure and properties of aluminum-air battery anode materials

Abstract

This study investigates the effects of Al–5Ti–B master alloy addition on the electrochemical properties and discharge performance of commercial pure aluminum (1060Al) in 4 M NaOH solution. The results show that the coarse branch-like α-Al grains are transformed into finer and smaller equiaxed grains, and the iron-rich phase are changed from long rod-like to small spherical grains. TiB2 particles introduce more heterogeneous nucleation sites in the α-Al crystals, resulting in an increased amount of grain boundaries in the aluminum matrix. There are more crystal defects at the grain boundaries than in the interior of α-Al grains, which provids more channels and energy for the reactions. This significantly increases the electrochemical activity of the aluminum alloy, causing the negative shifts for both the open circuit potential and the corrosion potential. The reduction in the size and change in the morphology of the iron-rich phase decreased the contact area between the iron-rich phase and the aluminum matrix, weakening the galvanic action between them. Meanwhile, the refinement of the α-Al grains decreased the potential difference between the interior and exterior of the grains, resulting in a reduction in the material corrosion current and an improvement in its corrosion resistance. Therefore, compared to the method of adding high hydrogen evolution potential elements to suppress hydrogen evolution reaction, the refinement of α-Al grains and the changes in the size and morphology of iron-rich phases due to the presence of TiB2 particles are the main reasons for improving the corrosion resistance and discharge performance of aluminum-air batteries in NaOH solution.