Improvement of aluminium foaming by powder consolidation under vacuum

Foamable AlSi11 precursors were uniaxially hot-compacted under vacuum and air and then foamed. We studied the influence of the compaction atmosphere on the foaming behaviour in situ by X-ray radioscopy. In vacuum-pressed precursors the growth of elongated bubbles was reduced, resulting in a larger expansion and more reproducible foaming due to improved consolidation. As a consequence, foams made from these precursors show a more regular pore size distribution than foams made from traditionally pressed precursors.