The effect of compaction method on the expansion and stability of aluminium foams

The foam expansion and collapse behaviour for heat treated Al-TiH2 precursors has been shown to be driven by the oxidation of the Al powder, which can, in moderation, improve the foam expansion and increase foam stability, and the premature loss of gas from the TiH2, which delays but decreases the foam expansion. The evidence presented indicates that as long as theoretical precursor densities > 99 % can be achieved, simultaneous heating and compaction are not required to achieve the best foaming behaviour. Instead, the oxygen or oxide content in the powder is critical and if the oxygen content in the atomised powder is in the range 0.3-0.4 wt.%, cold compaction is sufficient to produce foams which show expansions at least as good as those for precursors made by high cost hot working processes.