The present paper highlights results from the priority program "Cellular Metals" of the Deutsche Forschungsgemeinschaft (DFG SPP 1075). Micropores, which are created in foamable precursor material in initial foaming stages, are suspected to influence the pore structure to obtain a more homogenous and finer Al-foam. Micropores are expected to reduce the mismatch between foaming agent decomposition and matrix melting temperature. The presence of micropores in the initial foaming stage leads to a suppression of crack propagation and acts as a storage for premature gas release. In this study we exploited the high diffusivity of molten zinc in the Al-matrix for producing micropores in the initial foaming stage. Furthermore the presence of zinc reduces the melting point of the Al-matrix. Different zinc contents (0.5, 1.0, 2.0, 5.0 and 10.0 wt.%) as well as different Zn particle sizes ( < 40 μm, 120 μm and > 315 μm) were employed in this study. The produced foam was studied in different foaming stages by aid of light microscopy, scanning electron microscopy and X-ray micro-tomography. The results indicate that subsieve zinc ( < 40 μm) and Zn contents 1-2 wt.% result in a more homogeneous Al-foam. The mean material thickness is reduced by 25% and the distribution is shifted to lower thickness with narrow distribution.
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