Due to their low density, weight reduction of up to a maximum of 80% can be achieved with respect to the same volume of conventional metals. The mechanical behavior is strictly related to the morphology of the porosity and consequently to their production methods. The main properties of metal foams are their low density, high energy absorption in compression and crash tests, high acoustic and vibration absorption, high heat transfer coefficient, and high electrical and thermal conductivity. The main difference is the presence or absence, respectively, of pore interconnections. A first classification can be performed on the basis of their porosity: open or closed. Metal foams are cellular solids composed of a solid and a gas phase. The foam with truncated octahedron cells was found to show the highest absorbed energy/relative density ratio.
After that, the results obtained for mechanical performance during static compression tests with different geometry porosities are compared and discussed. The main production steps are examined at first. The main aspects on which we focus are the set-up of the process parameters and the characterization of the mechanical properties of the manufactured samples. These foam prototypes can find application in the automotive, civil and aeronautical fields due to their high surface/weight ratio, making them optimal for heat exchange and for the ability to absorb energy during compression. The next step consists of the gravity casting of the EN-6082 alloy in the plaster form, obtaining metal foams that are interesting from a technological point of view as well as with respect to their mechanical properties. The production process is articulated in many steps: PLA foams are inserted into an ultra-resistant plaster mix, after which the polymer is thermally degraded. This method combines the advantages of rapid prototyping with the possibility of manufacturing Al-alloy specimens with low time to market. Through CAD modeling, different geometries were replicated so as to get black PLA samples. With a double extruder 3D printer (FDM, Ultimaker S3, Utrecht, The Netherlands), it is possible to make polymer-based samples of the lost model. A flexible and versatile method for manufacturing open-cell metal foams, called lost-PLA, is presented in this work.
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