Foaming Agents for Powder Metallurgy Production of Aluminum Foam

Abstract

Metallic foams are commonly produced using hydride foaming agents. Carbonates are safer to handle than hydrides; however, their use in the powder metallurgy (PM) route to obtaining a fine and homogenous cell structure has not been evaluated. In this study, carbonates and hydroxides were investigated as foaming agents for the production of Al-Si-Cu alloy foams by the PM route. The thermal decomposition behavior of the foaming agents was evaluated in conjunction with the cell structure of the aluminum foams produced. From the results, it was clarified that a foaming agent that began decomposing after the matrix melted is required to obtain a fine and homogenous cell structure. The TiH2 foam formed under similar conditions was obviously different and had a coarse and rounded cell structure. MgCO3 and CaMg(CO3)2 were selected as suitable foaming agents for the Al-Si-Cu alloy. Once expanded, the CaMg(CO3)2 foam had a specific gravity of 1.19 and a homogeneous, fine and spherical cell structure.