Fabrication of Al foam without thickening process through melt-foaming method

By using calcium carbonate (CaCO3) powder as the blowing agent, Al foams with porosities of similar to 60 to 85% and pore size of similar to 1.5 mm were fabricated via melt-foaming method. Instead of adding a thickening agent to increase Al melt viscosity, a small amount of Mg ingot (5.0 wt%) was added first, and then Al melt was foamed by adding calcium carbonate via the impellor stirring. The effect of Mg addition on the gas release behavior of calcium carbonate in the Al melt was investigated. The compression behavior of fabricated Al foams was examined. The results show that the blowing gas is possibly from the reaction between Mg and calcium carbonate, and this reaction can produce solid oxides with micrometer level size, which leads to increasing the Al melt viscosity and is beneficial for inhibiting pores coarsening. Besides, the micrometer level cracks in the cell walls make the strength of Al foam decrease.