Casting of Aluminium Foam with Defined Porosity Using DoE

Closed cell aluminium foam offers an interesting combination of properties such as high energy absorption, stiffness, strength and low density. These properties give it great potential as an impact absorbing material which can be used in the automotive industry, military, civil engineering and others. To achieve these properties, the structure of the foam is important. The number, shape, regularity and distribution of pores are of great importance. A major disadvantage of aluminium foam is its low viscosity and consequently poor castability. Casting of aluminium metal foam is achieved by a thermally activated chemical reaction of the foaming agent calcium carbonate (CaCO3). Different amounts of foaming agent and reaction times have been used to achieve defined porosity. With regard to process stability and manufacturing cost, optimal parameters to achieve defined porosity were found using DoE (Design of Experiment) methodology. As a result, longer agitation times were found to produce more homogeneous foams as the calcium carbonate powder was better distributed, consequently more calcium carbonate powder needs to be added as it reacts and is consumed when in contact with the melt. Experiments were performed using gravity casting and simple shapes can be made this way. Efforts are currently being made to establish a manufacturing process that can be used to produce castings with defined geometry.