Aluminium foam with sub-mm sized cells produced using a rotating gas injector

Abstract

Closed-cell solid aluminium alloy foams should ideally contain small and equally sized cells for the sake of better and more predictable mechanical properties, but real foams generated by injection of gas into melts usually exhibit a broad distribution of cell sizes and shapes. Here we investigate how gas bubbles in an aluminium alloy melt containing stabilizing SiC particles can be created in a controlled way by letting the injector move on a circular orbit through the melt at different velocities and adapting the gas flow. The structures of the resulting solidified foams are characterized by X-ray tomography. We identify conditions that allow us to obtain near-monodisperse foams with cell sizes below 1 mm and are able to reduce the content of SiC particles from the usual 20 vol% to 8 vol%.