Computational Fluid Dynamic Simulation of Sedimentation Process; Optimisation of Inclusion Control in Recycled Aluminium Alloys

The transition toward net-zero manufacturing increased the use of recycled aluminium alloys in high-performance applications. However, their wider adoption, particularly in aerospace manufacturing, is limited by the presence of inclusions and intermetallic compounds that reduce melt cleanness and mechanical integrity. This study investigates the sedimentation behaviour of inclusions in recycled A356 aluminium alloy using computational fluid dynamics simulation as part of the UltraCleanCAST DLMM project. The simulation model incorporated alumina and Fe-rich intermetallic inclusions with diameters between 25 µm and 1000 µm and densities of (2560, 3338, and 3990) kg/m³. Simulations were conducted at flow rates of (50, 100, 180, and 500) kg/h under different baffle configurations, temperature gradients up to 100 °C and localised heating conditions within a newly designed launder.

The results show that inclusion sedimentation is sensitive to both flow rate and temperature gradient. Previous studies showed that flow rates below 100 kg/h promoted greater inclusion settling, however, localised heating applied at the middle and outlet sections of the launder further improved sedimentation efficiency by ~ 66 %. Under optimal combined conditions, the overall inclusion sedimentation efficiency increased by ~ 88 %.

These quantitative results provide a basis for optimising launder design and operating parameters for sedimentation-based purification. The study supports the development of a low-energy purification strategy for secondary aluminium casting, enabling cleaner production of recycled alloys for aerospace applications.