| ABSTRACT: | QUANTITATIVE ANALYSIS OF SPATIAL PORE-PARTICLE-CORRELATIONS IN METALLIC
FOAMS
A. Haibel, A. Rack, and J. Banhart
Hahn - Meitner - Institut Berlin, Berlin, Germany
Metallic foams are highly porous materials with interesting properties. They are characterised by low
density, high specific stiffness, and high energy absorption capability. Therefore they become more and
more popular for industrial applications. In order to produce metallic foams with reproducible macroscopic
properties, the precise knowledge of their microscopic structure is needed. Our research aims at the
understanding of the physical mechanisms during the foaming process and on the optimisation of the
manufacturing parameters. The objective is to adjust and improve the pore size distribution, the wall
thickness, the density, and the homogeneity.
One foam production route is to add a blowing agent, usually titanium hydride, into the precursor material.
After heating up the precursor to above the decomposition temperature of the blowing agent and the melting
temperature of the metal, hydrogen is released in the melt and a porous structure is generated. To achieve a
sufficient stability of the pores during the foaming process, micrometer-sized non-soluble silicon carbide
particles can be admixed. Due to their partial wetting property they accumulate on the pore surfaces and
stabilise the cell walls.
The influence of both components, blowing agent and non-soluble particles, on the foaming structure was
investigated non-destructively using synchrotron tomography. Varying the blowing agent particle size, the
correlation with the pore size distributions was studied.
To investigate the rearrangement process of the cell wall stabilisers we measured their 3d spatial distribution
in an unfoamed cast solid aluminium precursor, in the fully foamed liquid state, and in the solidified final
state of the foam. The tomographic investigations were carried out using the beamline of the Federal
Institute for Materials Research and Testing (BAM) at BESSY synchrotron, Berlin. A special 3d dilatation
algorithm yields quantitative results for the spatial pore-particle-correlation.
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