The objective of this study was to investigate the effects of the number of roll-bonding cycles and Al2O3 powder addition on the porosity and pore morphology of aluminum foams produced using the Clad-Chip Extrusion (CCE) precursor method. Two A1050 aluminum sheets were stacked with TiH2 powder as a foaming agent between them and subsequently roll-bonded to produce a laminated sheet. This laminated sheet was cut into squares approximately 10 mm on each side to obtain clad chips. Al2O3 powder, serving as a bubble stabilizer, was mixed with these clad chips, and the mixture was then extruded to obtain a CCE precursor. For comparison, a CCE precursor without Al2O3 addition was also produced. Additionally, a CCE precursor was produced by extruding two-cycle roll-bonded clad chips. Foaming tests were carried out on all precursors to evaluate the resulting foam porosity. The obtained foams were cut in half, and their cross-sections were photographed and image-analyzed to determine the pore morphology. The porosity of the foam made from one-cycle roll-bonded clad chips was similar to that from two-cycle roll-bonded clad chips. Furthermore, the porosity and pore size of the foams containing Al2O3 powder were found to be significantly lower in comparison to those without Al2O3 powder. This reduction is primarily attributed to the Al2O3 particles agglomerating at the low-strength bonding boundaries during extrusion. This agglomeration further reduced the bonding strength and contributed to the leakage of H2 gas, thus limiting their intended contribution as a bubble stabilizer. Despite this limitation, the Al2O3 addition was found to stabilize the melt and prevent foam collapse after the matrix melted.
Suzuki et al. (Tue,) studied this question.