Failure analysis of cast open-cell iron based foams from the submicron to the macro-scale

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Open cell steel foams are promising candidates for impact absorbing applications. They are generally inexpensive, possess a low density, and, as compared to aluminium foams, they combine a higher strength with high ductility and toughness. Former work, nevertheless, nearly always focuses on closed- and open-cell aluminium foams. As aluminium alloys have a profoundly different deformation and failure behaviour as compared to steels, and because the knowledge on bulk steel cannot simply be transferred to foams because of the small size of the struts and the different casting conditions, further development of steel foams relies on improved knowledge on the microstructure/mechanical-property-relationships of these foams. In this study, we therefore plan to investigate the mechanical behaviour and the microstructure of a novel cast steel foam and its struts on different length-scales from the sub-µm to cm range, by combination of mechanical testing of foams and single, extracted struts with 2D microscopy and 3D tomography methods. The results will be compared with those from former work on austenitic steel foams, and correlations between the different microstructures and the foam properties will be deduced. The relationships between the strut microstructure and the mechanical properties on the different length-scales will be integrated and used to suggest possible improvements in the microstructure and the production process of steel foams.