Effect of powder oxide content on the expansion and stability of PM-route Al foams

The oxide content ill Al powders has been found to have a significatant effect oil the expansion and stability of foams made via a PM route. With low oxide contents to (O < 1 0.3)wt%) expansion is moderate and the foam is unstable. Larger expansions, improved foam stability and more homogeneous foam structures are achieved if the amount of oxide in power is moderate (0 = 03-0.6 wt%). Foaming precursors with excessive oxide contents (O > 0.6 wt%) results in small expansion but very stable foam structures. Oxides were observed to form clusters of crumpled films. which at higher levels form a network which restricts the drainage of liquid from the cell walls an Plateau borders. but which also inhibit foam expansion. Oxide clusters in the cell walls lead to a decrease in the minimum cell wall thickness. resulting in an increase in foam expansion. (c) 2005 Elsevier-Inc. All rights reserved.