Al-foams as cores in casting technologies

Metal foams, or metallic porous materials, are a new class of materials which have lower densities compared with their dense metallic counterparts. Many applications of metal foams have been widely developed in industries because of their advantageous properties, such as lightweight, good energy absorption ability, higher stiffness, recyclability and so on. Now, the main applications are in three fields: Architecture, Automotive and Medical. In this thesis, the characteristics of Al-foams and the possibility to use them as cores in casting technologies are studied. For this last point, foams with different densities were inserted into the casting die and aluminum alloys were cast around the foam cores. At first non-inserted foams were characterized in terms of porosity, skin and wall thickness and microstructure by means of optical microscopy. Foam density was evaluated through weight and volume measurements. Moreover, chemical composition and morphology of the foam surface (outer skin) and cross section was investigated by means of Scanning Electron Microscopy (SEM) equipped with Energy Dispersive Spectroscopy (EDS). Finally, thermal conductivity of foams samples was measured by the hot disk technique. After insertion in casting optical microscopy was used to investigate the degree of foam infiltration, the eventual foam-dense metal bonding and the foam and dense metal microstructure.