Effect of Compaction Pressure on Microstructural, Mechanical, and Thermal Properties of Aluminum Foams Processed Through Space-Holder Technique

Al foam samples were prepared by following the space-holder route using spherical shape carbamide as space-holders and application of various compaction pressures (CPs) (200, 300, 400, and 500 MPa). Al foams prepared with CP 300 MPa (CP300) showed uniform pore distribution with a smooth pore-wall surface and dense matrix microstructure without any internal cracks in the pore walls. However, in case of Al foams made with CP 200 MPa (CP200), 400 MPa (CP400), and 500 MPa (CP500), there were surface irregularities and micro-voids due to cracks in the pore walls. The XRD analysis of sintered Al foam confirmed the absence of any additional phase formation. Al foams with CP300 have also shown higher plateau stress (18 ± 0.8 MPa), energy absorption (11.86 ± 0.5 MJ/m3), improved Young’s modulus (3.03 ± 0.15 GPa) and lower densification strain (0.54 ± 0.0127) than other foams. Al foams made with CP300 demonstrated higher thermal conductivity ( 35 ± 1.48 W/m K) as compared to other foams. From the microstructural, mechanical, and thermal studies, we can conclude that 300 MPa is an optimum compaction pressure for producing high quality Al foams when irregular Al powder of average size 35 µm and carbamide space holder with the size of 1.60-2.0 mm are used as raw materials. The effect of compaction pressure on microstructure and mechanical properties was discussed with clear emphasis on underlying principles.