Production, Characterisation and Testing of Open Cell Al Foams Manufactured by Molten Metal Infiltration of Porous Salt Bead Preforms

Al foams with an open cell structure have been manufactured by infiltration, facilitated by pressure-assisted vacuum investment casting of molten Al into preforms made by the compaction of porous spherical beads made from fine salt powder. The preform and resulting foam density decreased with increasing compaction pressure and the foam density increased with increasing infiltration pressure. For low pressure infiltration, and high density preforms, salt dissolution was rapid. Infiltration of molten Al occurred into the beads and for high density preforms and higher infiltration pressures, the volume of metal in the beads exceeded that in the cell walls, drastically decreasing the NaC1 dissolution rate. Despite the non-optimum distribution of metal in the foam structure, the magnitude and density dependence of the yield stress were comparable with those for pure Al foams reported in similar studies.