Effect of Space Holder Size on Microstructure and Mechanical Properties of Aluminum Foam

Metal foams, unlike conventional metals, possess a high volume fraction of pores, which imparts a unique combination of lightweight properties, high strength, and stiffness, alongside excellent mechanical performance. One of the key methods employed in the fabrication of aluminum foam is the space holder technique, which allows for precise control over porosity and pore size. In this study, aluminum foams with 80% porosity were fabricated using the space holder method, varying the size of the space holder particles to compare and analyze their properties. The foams were sintered using spark plasma sintering, and the resulting microstructure was examined via field emission scanning electron microscopy. The analysis confirmed the successful formation of inter-particle necking, indicating proper sintering. Additionally, micro-computed tomography was utilized to investigate the internal structure, revealing details such as pore size, cell wall thickness, and overall porosity. The results showed that both pore size and cell wall thickness decreased with smaller NaCl particle sizes. Compression tests were conducted to assess the mechanical properties of the foams. Factors such as porosity, pore size, and cell wall thickness were found to significantly influence the compressive strength. Notably, as the NaCl particle size decreased, a corresponding reduction in compressive strength was observed, likely due to the effect of reduced cell wall thickness. Finally, a predictive model for compressive strength as a function of space holder size was proposed.