Synthesis and Characterization of Al Chip-Based Syntactic Foam Containing Glass Hollow Spheres Fabricated by a Semi-Solid Process

Abstract

In this study, aluminum (Al) chip matrix-based synthetic foams were fabricated by hot pressing at a semi-solid (SS) temperature. The densities of the foams ranged from 2.3 to 2.63 g/cm3, confirming that the density decreased with increasing glass hollow sphere (GHS) content. These values were approximately 16% lower than the densities of Al chip alloys without GHS. The Al chip syntactic foam microstructure fabricated by the semi-solid process comprised GHS uniformly distributed around the Al chip matrix and a spherical microstructure surrounded by the Mg2Si phase in the interior. The resulting spherical microstructure contributed significantly to the improvement of mechanical properties. Mechanical characterization confirmed that the Al chip syntactic foam exhibited a compressive strength of approximately 225–288 MPa and an energy absorption capacity of 46–47 MJ/M3. These results indicate higher compressive properties than typical Al syntactic foam. The Al chip microstructure, consisting of the Mg2Si phase and GHS, acted as a load-bearing element during compression, significantly contributing to the compressive properties of the foam. An analysis was performed using an energy-dispersive spectrometer to validate the interfacial reaction between the GHS and the matrix. The results showed that MgAl2O4 was uniformly coated around GHS, which contributed not only to the strength of the matrix, but also to the mechanical properties via the appropriate interfacial reactive coating.