The role of hot extrusion in improving electrochemical properties of low-cost commercial Al alloy as anode for Al-air battery

Abstract

• Common hot extrusion was applied to modify the microstructure of Al6063. • Hot extrusion was able to refine α-Al grains and large-sized AlFeSi phase. • Hot extrusion induced the significant improvement in electrochemical performance of Al6063. Hot extrusion (HE) was applied in the treatment of low-cost commercial Al6063 alloy containing impurity iron (Fe) element (0.12 wt%) with the aim of decreasing the self-corrosion and optimizing the discharge performance of Al6063 alloy as an anode for Al-air battery. Experimental results showed that HE effectively refined the α-Al grains as well as the coarse AlFeSi phase along the grain boundaries and further led to the intragranular distribution of AlFeSi phase. The electrochemical tests proved that the corrosion resistance of Al alloy after HE treatment was enhanced. Combined with the surface analysis of Al anode after discharge, the immersion test suggested that the corrosion pits were prone to occur near the AlFeSi phase rather than at the grain boundaries and the distribution of AlFeSi phase at grain boundaries could accelerate the corrosion process, indicating that the HE induced improvement in corrosion resistance of Al alloy was attributed to fragmentation of AlFeSi phase and its distribution within grains from grain boundaries. Furthermore, owing to the increased grain boundaries and delayed corrosion process, the average discharge potential of Al anode increased from 1.1737 V to 1.1914 V while the energy density as well as the anode efficiency of which were improved by 65.39% and 62.95%, respectively. This research provided an effective approach to the expansion usage of low-cost commercial Al alloys as the potential anode materials for Al-air batteries.