Three dimensional forming of compressed open-cell metallic foams at elevated temperatures
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2015 Elsevier B.V. Metallic foams represent a unique class of lightweight materials which possess an attractive combination of physical, mechanical, thermal, electrical and acoustic properties. They represent huge potential for lightweight structural applications in several key industries including automotive, fuel cells, advanced heat exchangers and concentrated solar power plants. Currently, the products made of metallic foams are fabricated into the final shape by a casting based foaming process, thus limiting their widespread use. Therefore, it is important to develop effective manufacturing processes to shape metallic foams sheets into complex geometries. In this work, we successfully demonstrate a novel approach to shape as-compressed foam AA6101 aluminum alloy sheets into three dimensional near-net shape parts by pneumatic forming at elevated temperatures. The deformation behavior and failure characteristics of aluminum foams under uniaxial tensile loading at various strain rates and temperatures in the as-cast and as-compressed condition were studied. Our results showed that in as-compressed condition the aluminum foam possesses 8-9 times higher tensile strength as compared to the as-cast condition at room temperature. The reduction in thickness in the bulge formed foam specimen starting from an as-compressed condition was 20%, in comparison to 80% reduction observed for the as-cast condition. These initial results demonstrate the possibility of applying this technique to form as-compressed metal foam sheets into complex shapes without causing significant densification that can help maintain good thickness uniformity and homogeneity of pore distribution in formed parts.
