Laser surface melting of AA6061 with Fe and Zn impurities

Increased adoption of recycled aluminum (Al) alloys can provide economic and environmental benefits through vehicle lightweighting, decreased fuel consumption, and reduced greenhouse gas emissions, however, broader implementation is hindered by impurity element accumulation, as increased scrap can result in compositional drift of alloy streams, leading to degraded mechanical and electrochemical properties. This work investigates the use of rapid solidification processing (RSP) to increase adoption of recycled Al through the formation of non-equilibrium and metastable phases, refinement of microstructural features, and increased element solubility. Cast ingots of Al alloy 6061 (AA6061) were produced with iron (Fe) and zinc (Zn) additions ranging from 0 to 1 wt%, simulating recycling impurities. Thermodynamic simulations were used to predict crack susceptibility. Laser surface melting (LSM) trials were performed on plates from each ingot to generate rapidly solidified microstructures. The simulation predictions and microstructure results suggest that alloy impurity influences the cracking behaviour observed in the resolidified melt pools, with Fe addition having a positive effect on cracking behaviour, while Zn tended to increase simulated crack susceptibility, regardless of Fe content. The results suggest that RSP techniques can be implemented as an impurity control method in recycled Al alloys, supporting its use for industry applications.