Process Development and Material Characterization for the Novel Melt Processing of Near Net Shape Foam Parts

In this paper a new processing technique for producing closed cell net shape aluminium foam parts via the melt route developed by Hütte Klein-Reichenbach and ARC Leichtmetallkompetenzzentrum Ranshofen is presented.

The new method facilitates the simplest method of producing a metallic foam by bubbling gas through a molten metal matrix composite (MMC). The resulting stable liquid aluminium foam is guided into a mould, where the foam is solidified. The bubble size of the produced foam can be controlled by the new nozzle design of the gas bubbling equipment according to physical principles of bubble formation in molten metals. Homogeneous cellular structures are achieved for mass densities of 0,1 to 0,6 g/cm³ and narrow cell size distribution of 3 to 15 mm +/- 2 mm.

An important advantage of aluminium foam produced with this technique is the freedom it offers with the regard to variations of the process parameters and the alloy. In this way, it is possible to adjust the properties of the produced aluminium foam. A first characterization of manufactured foam samples with different densities is gained through compression tests. The cellular structure such as density distribution and cell wall thickness, are investigated by computed X-ray tomography and image analysis.