Processing, characterization and mechanical properties of welded steel hollow sphere-reinforced aluminum matrix composites

Metal matrix composites filled with metal hollow spheres have attracted much attention for their benefits, such as lightweight, load-bearing capacity and energy absorption. This study examines the structural and mechanical properties of the hollow sphere-reinforced composite (HSRC) fabricated by the pressure-less molten infiltration, using more common welded steel hollow spheres as reinforcements and aluminum alloy as the matrix. The microstructure properties of HSRC have been tested by an X-ray electron probe micro-analyzer. The interface layer with a thickness of 20–25 μm was found to form between the hollow spheres and the matrix, effectively maintaining the tight bonding. The quasi-static compressive properties of welded steel hollow spheres and HSRCs were examined using a universal material testing machine. The stress–strain curves of HSRCs exhibited the typical behavior of metallic-based porous material. The functionally graded (FG) HSRC performed better on mechanical properties than uniform HSRC. These welded hollow spheres displayed high load-bearing capability with stable deformation mode, which contributed substantially to the uniform deformation of HSRC without any shear bands. The plateau strength-to-density ratio of the uniform and FG HSRC specimen is 22.11 MPa (g cm −3 ) −1 and 30.91 MPa (g cm −3 ) −1 , respectively. The specific energy absorption (SEA) at 60% strain is 19.4 J g −1 and 22.9 J g −1 , respectively, showing the great potential of HSRC for the development of energy absorption and lightweight impact protection.