The Influence of Foaming Agents on Aluminium Foam Cell Morphology

Abstract

The choice of foaming agent and its mass fraction significantly affect the size and number of metal foam cells. The powder metallurgy process was used to produce aluminium foams with the addition of various foaming agents: titanium hydride (TiH2) and calcium carbonate (CaCO3). TiH2 was added in an amount of 0.4 wt.%, while the quantity of CaCO3 varied between 3 and 5 wt.%. The produced foams, with approximately the same degree of porosity, were scanned using a non-destructive computed tomography method. The number, size, equivalent diameter, sphericity, and compactness of cells were analysed on the obtained three-dimensional models. The results showed that foams foamed with TiH2 have much larger cells compared to CaCO3 agent. By considering the influence of CaCO3 fraction on the morphology of aluminium foam, it follows that a smaller quantity of CaCO3 (3 wt.%) provides a macrostructure with smaller cells. Samples with five wt.% CaCO3 contain slightly larger cells but are still much smaller than foams with TiH2 foaming agent at the same degree of porosity. The sphericity and compactness indicate that TiH2 foaming agent forms cells of a more regular shape compared to CaCO3 agent.