Alexander Martin Matz

Mesostructural Design and Manufacturing of Open-Pore Metal Foams by Investment Casting

The present paper describes the manufacturing process of open-pore metal foams by investment casting and the mesostructural/morphological evolution resulting from a new technique of modifying the precursor. By this technique, the precursor is coated with a polymer layer whereby a thickening of the struts occurs. Relative densities in the range of of open-pore metal foams can be achieved with high accuracy. The samples investigated have pore densities of ppi, 10 ppi, and 13 ppi. The relevant processing parameters needed for a homogenous formation of the polymer layer are determined for two different coating materials and the resulting open-pore foam’s mesostructure is characterized qualitatively and quantitatively. The alloy used for investment casting open-pore metal foamsis AlZn11. The microstructural evolution of these foams is evaluated as a function of the mesostructure. Differences in the microstructure are observed for foams with low and high relative densities and discussed in terms of cooling subsequent to investment casting.

Effective thermal conductivity of open-pore metal foams as a function of the base material

Abstract The effective thermal conductivity of open-pore metal foams in combination with the fluids air and water have been investigated in an extended range in relative density and selection of material. This study is conducted to estimate the influence of the thermal conductivities of the combination “metal foam — fluid” λs and λfl on the effective thermal conductivity λe of the open-pore metal foam. Therefore, open-pore metal foams (ρrel = 12.7 % in average) of different base materials are manufactured by respect of significant differences in the thermal conductivity of their bulk material in a range of 24.80 W × (m × K)−1≤λs≤ 402.13 W × (m × K)−1. These samples are saturated by air and water and the effective thermal conductivities of the corresponding combinations are determined. The thereto used method is a transient one and is based on the theory of inturbide temperature fields. The impact of the fluid type on λe is evaluated and its dependence on λs is identified, resulting in a simple expression for estimating the effective thermal conductivity as a function of λfl, λs and ρrel applicable for air and water.

Microstructural Characterization of Open-Pore Metal Foams of Pure Metals

Abstract This work presents open-pore metal foams made by investment casting from several pure metals. The resulting microstructure and its morphology will be characterized and compared to the microstructure of permanent mold cast round specimens. In addition to their manufacture, the preparation of the different samples for microstructural characterization is outlined. Finally, the individual microstructures are analyzed and compared by means of light microscopy and under consideration of relevant parameters. The comparison of metal foam and round specimen microstructures yields significant differences in the microstructural development.

Heat propagation in computer designed and real metal foam structures

Purpose The purpose of this paper is to demonstrate a method for modeling of cellular structures by means of Voronoi tessellation and to conduct a validation by comparison with real metal foam structures. Design/methodology/approach Heat propagation behavior of open-pore metal foams is studied for both experimental as well as computer-modeled structures showing excellent agreement. The 3D open-pore structure of the real foam is reconstructed from 2D light microscope images in-depth. Findings An algorithm to create synthetic open-pore foam structures has been developed. Originality/value The algorithm for modeling synthetic open-pore cellular structures allows the random distribution of the individual pores close to reality.

Analysis and 3D-Modelling of Open-Pore Metal Foams Using Binarized Light-Optical Microscopy In-Depth Microsections

Abstract Open-porous metal foams are cellular structures that can be defined, in simplified terms, as interwoven networks of metal ligaments that are surrounded by a fluid (liquid or gaseous). They are characterized by a very low relative density of usually 4 to 12% of the density of a solid composed of an identical base material. As such they have a small volume along with a very large surface area, providing for numerous interesting physical properties with resulting practical applications. A detailed description of the physical properties of these materials essentially requires a characterization of their geometric structure. Within the scope of this work, microsections of these foam structures are captured in a defined depth distance of sz≤0,5 mm. In the course of the experiment, these microsections are software-converted to binary images. They are optimized in a way that artifact characteristics, which would have a negative effect on the analysis, converge to a minimum. Based hereon, it is now possible to generate realistic 3D models of individual microsections, allowing for a three-dimensional measurement of the material. Furthermore, binary format microsections allow for determining miscellaneous statistical characteristic values of the examined foam structures. Based on these results, it is consequently very easy to draw conclusions on the geometry of large-dimensional foam structures. When varying individual characteristic parameters, such a database also provides the possibility to generate differing geometric structures, which, in turn, provide for a sound basis in order to create scalable simulation models.