Effects of stirring speed and flux composition on the recycling of aluminium foams

Abstract

Owing to the excellent performance of aluminium foam in transportation, construction, and aerospace applications, their production has increased rapidly in recent years, leading to the accumulation of an increasing quantity of aluminium foam scrap and used aluminium foams. An efficient recycling process for these products is urgently required for resource conservation and environmental protection. In this study, a flux-covering method is employed to recycle aluminium foams. The effects of stirring speed and flux composition on the recycling process were investigated. An orthogonal test was performed to determine the optimal flux parameters for NaCl, KCl, and NaF. The microstructures of aluminium foam and recycled aluminium were observed using scanning electron microscopy and optical microscope, respectively. Phase compositions of foams, flux, recycled aluminium, and slag were analysed using x-ray diffraction. The results showed that the recovery was improved with increasing stirring speed, and the optimal stirring speed was 150 r·min−1 under the present conditions. In addition, the composition of the flux exhibited a significant impact on the recovery. The recovery reached 86.35% when the NaCl, KCl, and NaF concentrations were 15, 15, and 5 wt%, respectively. The mechanisms of recovery improvement were discussed in terms of the primary crystal temperature of flux as well as the thermodynamics and kinetics of the impurity removal.