Optimisation of compaction and liquid-state sintering in sintering and dissolution process for manufacturing Al foams

The effects of the compaction and liquid-state sintering conditions on the structure of the resultant Al foams manufactured by the sintering and dissolution process have been studied. The cell morphology and size of the final Al foam closely match those of the NaCl particles used. The foam porosity is 2–4% higher than the initial volume percentage of NaCl in the Al/NaCl powder mixture due to the contributions from green porosity and shrinkage. The microstructure of the Al matrix is characterised by an interconnected metallic framework with the presence of discontinuous interstices and fine voids as well as primitive particle boundaries in the cell walls. The optimum ranges of compaction pressure and sintering temperature are 200–250 MPa and 670–680 °C, respectively. Adding elemental Mg powder in the compacts has little effect on sintering. Adding elemental Sn together with Mg powders creates a densified Al matrix.