Abstract
Metallic foams are commonly produced using titanium hydride as a foaming agent. Carbonates produce aluminum foam with a fine and homogenous cell structure. However, foams produced using carbonates show marked shrinkage, which is clearly different from those produced using titanium hydride. It is essential for practical applications to clarify foam shrinkage and establish a method of preventing it. In this research, cell structures were observed to study the shrinkage of aluminum foam produced using carbonates. The cells of foam produced using dolomite as a foaming agent connected to each other with maximum expansion. It was estimated that foaming gas was released through connected cells to the outside. It was assumed that cell formation at different sites is effective in preventing shrinkage induced by cell connection. The multiple additions of dolomite and magnesium carbonate, which have different decomposition temperatures, were applied. The foam in the case with multiple additions maintained a density of 0.66 up to 973 K, at which the foam produced using dolomite shrank. It was verified that the multiple additions of carbonates are effective in preventing shrinkage.
Highlights
Metallic foams have unique properties, such as low density, good energy-absorbing capability, and low thermal conductivity
We have studied the principle of foaming by carbonates, and found that dolomite and magnesium carbonate are suitable foaming agents for AlSiCu alloy
It was assumed that cell formation at different sites is effective in preventing shrinkage, even if cell connections are formed
Summary
Metallic foams have unique properties, such as low density, good energy-absorbing capability, and low thermal conductivity. One of the manufacturing methods for metallic foams is the Fraunhofer method. This method uses a typical powder metallurgy (PM) route [1] that entails the hot extrusion of an aluminum matrix powder and a TiH2 to make precursor, the resulting product of which is heated in a closed die to produce foam for near-net shaping. TiH2 is a popular foaming agent because of its decomposition temperature, which is close to the melting temperature of aluminum alloys. One of the authors presented carbonates as alternatives to TiH2 [2], because they are inexpensive
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