Production of Open-Cell Aluminum Foams from Recycled Alloys by Gravity Melt Infiltration Casting
摘要
This work presents a simple gravity melt infiltration casting route for producing open-cell aluminum foams using recycled aluminum alloys and NaCl space-holder particles. The process enables the fabrication of porous structures without external pressure, gas injection, or chemical foaming agents, as is commonly used in conventional aluminum foam processing. Four recycled aluminum feedstocks were evaluated, including cylinder heads, machining shavings, beverage cans, and window frames, to assess the robustness of the casting process when using heterogeneous raw materials. NaCl particles with irregular polyhedral morphology and sizes between 13 and 15 mm generated foams with interconnected porosity ranging from 55.0 to 59.1 vol.% and equivalent pore diameters of approximately 7 mm. The melt infiltration process showed stable filling behavior and good structural integrity during casting and space-holder removal. Microstructural characterization by SEM and EDS revealed Si, Cu, and Mg-rich intermetallic phases distributed within the α-Al matrix, with morphologies that depended on the composition of the recycled alloys, and a low fraction of microporosity (~0.15 %) within the cell walls. Compressive strengths up to 20.4 MPa and hardness values of 104 HV were obtained for foams containing higher intermetallic fractions, while foams with cleaner matrices showed improved ductility and energy-absorption capacity up to 13.8 MJ m−3. The mechanical response was further interpreted using the Gibson–Ashby model for open-cell foams, showing that deviations between experimental and predicted strengths are strongly influenced by microstructural features such as intermetallic content and matrix ductility. The results demonstrate that gravity melt infiltration casting offers a practical and scalable route for producing open-cell aluminum foams from recycled aluminum with tunable mechanical performance.