A novel iron-based open cell foam, based on reticulated Polyurethane (PU) foam, was produced by a modified investment casting process. The microstructure and failure of foams and struts were characterized by using LM, SEM, nanoindentation and SR-µCT. Metal foams were compressed and extracted single struts were pulled quasi-statically in the SEM. Due to the low preheating of the mould, a large cooling rate is resulted which leads to formation of superfine graphite in the ferritic matrix. In the microstructure of gray cast iron foam struts two types of graphite were present; superfine graphite particles between the dendritic arms and comparatively coarser coral graphite particles in the ferritic matrix. The distribution of those two graphite types is quite heterogeneous and leads to a large scattering in the mechanical properties of the struts. The large C content (CE is 4.3) of microstructure reduces the ductility of the struts leading to serrations in the stress-strain curves. This results in a relatively low energy absorption efficiency of below 50 %. Furthermore, production defects such as micropores and oxide particles are stress-raisers and thus act as crack initiation sites during bending of the struts in the foam. Gray cast iron foam was successfully fabricated but further improvement in the process is needed for further development of iron-based foams.
Keywords: cast iron, metal foams, casting, SR-µCT