Effect of Different Upper Side Types of Plaster Molds on the Pore Formation of Al Foams via Upward Foaming Method

Fabrication of Aluminum foam with near net shape has been investigated by powder metallurgy method and conventional pouring method. PM method is good for fabrication of near net shape foam, but it needs high cost compared with pouring method. More cost-effective methods are needed to make near net shape al foam to be applied various field. Therefore, novel method for fabrication Al foam was researched in this paper. In order to prepare near shape Al foams with homogeneous pore structures, the so-called upward foaming method was designed and applied. By using this method, two kinds of molds were designed, one is stainless mold used for melting and foaming Al and another is the plaster mold with near net shape. The fabrication procedures of near net shape Al foam are as following: (1) a quantity of Al ingot was melted in the stainless mold; (2) Ca particles was added in the Al melt to increase its viscosity; (3) TiH2 was introduced in the thickened Al melt to make melt being foamed; (4) the plaster mold was put on the stainless steel one to make enlarging Al melt foam fill with the plaster one; (4) the plaster mold was removed and was cooled. In this study, in order to get near net Al foam with relative good pore structures, the plaster molds were designed with three different upside styles and their effects on the pore structures (pore size, porosity and cell wall thickness) of Al foams were investigated. The results showed that the Al foam had the relative good pore structures when the plaster mold with a void was applied.