Superplastic Forming and Foaming of Cellular Aluminum Components

Abstract

Liquid and semi-solid state foaming processes have been widely used as a manufacturing method of closed-cell metal foams. These metal foams usually have large pores as well as high porosity. Large pores and inhomogeneous pore distribution often cause a decrease in mechanical properties. Therefore, microcellular foams are desirable for engineering applications. In the present study, solid-state foaming process under superplastic conditions is examined in order to manufacture microcellular aluminum foams. The superplastic flow during the high temperature foaming accelerates the foaming rate and increases the porosity. Commercial SP5083 aluminum alloy sheets were used as a starting material because they are typical superplastic material. Preform sheet containing titanium hydride particles was produced through accumulative roll-bonding (ARB) processing. Heating the preform sheet under superplastic conditions, we obtained aluminum foam with small oblate pores. The thermal conductivity was quite small because of the oblate pore shape. Superplastic flow enabled to produce a thin sandwich panel and porous bulge structures. These panel and bulge with oblate spheroidal pores parallel to the surface are industrially important because of their excellent thermal insulation. Present experimental results of superplastic forming and foaming (SPFF) processing has potential for near net-shape forming of microcellular aluminum foams.