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

开孔泡沫钢是很有前途的冲击吸收应用的候选者。它们通常是便宜的，具有低密度，并且，与泡沫铝相比，它们结合了更高的强度，高延展性和韧性。然而，以前的工作几乎总是集中在闭孔和开孔泡沫铝上。由于铝合金与钢相比具有截然不同的变形和破坏行为，并且由于支柱尺寸小和铸造条件不同，关于大块钢的知识不能简单地转移到泡沫钢中，因此泡沫钢的进一步发展依赖于对这些泡沫的微观结构/机械性能关系的改进知识。因此，在这项研究中，我们计划通过结合泡沫和单个提取支柱的力学测试，利用2D显微镜和3D断层扫描方法，研究一种新型铸钢泡沫及其支柱在亚微米到厘米范围内的不同长度尺度上的力学行为和微观结构。将所得结果与以往有关奥氏体泡沫钢的研究结果进行比较，并推导出不同组织与泡沫性能之间的关系。在不同长度尺度上，支撑结构的微观结构与力学性能之间的关系将被整合，并用于建议在微观结构和泡沫钢的生产过程中可能的改进。

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.