The research sited in this paper involves the development of new closed cell metal foam composite materials using powder metallurgy (PM) and gravity casting techniques. The foam is comprised of steel hollow spheres packed into a random dense arrangement, with the interstitial space between spheres occupied with a solid metal matrix. Using a casting technique, an aluminum alloy infiltrates the interstitial spaces between steel spheres. In a powder metallurgy method, steel spheres and iron powder are sintered to form a solid, closed cell structure. The measured densities of the Al-Fe composite foam and iron foam are 2.4 g/cm3 and 3.2 g/cm3, with relative densities of 42% and 41% respectively.
The hollow sphere metal foam composite materials developed in this study displayed superior compressive strength as compared to hollow sphere foams currently being produced. The compressive strength of the cast Al-Fe foam averaged 67 MPa over a region of 10 to 50% strain, while the steel PM foam averaged 45 MPa over the same strain region. Densification began at approximately 50% for the cast foam and 55% for the PM foam.