Metallic foams

INASMET Technological Centre is working on a project to develop metallic foams. Metal foams and cellular metals have become one the preferred research fields in mew materials in recent times. Given their special structure and extreme lightness, they have enormous potential for use in a never-ending list of applications in diverse industrial sectors.

Metallic foams are, as their name indicates, metallic materials with a porous structure. They can take either the form an open structure of interconnected pores, similar to a bath sponge or a closed structure of pores not connected to each other.

They have very low density (between 0.03-0.2 g/cc) at the same time showing some of the properties of the metal of which they are made up, together with other characteristics due to its particular structure. Thus, they are materials with a combination of very special physicochemical and mechanical properties, to such an extent that the series of properties they show is not currently covered by other materials, at the same time as they improve their respective applications.

In fact, the term best suited to define this type of materials would be ’multifuntionality’. They can be used in structural applications (given their excellent rigidity/weight ratio, durability, etc.) or in energy absorption of impacts and explosions (due to their capacity for isotropic absorption of energy at low and constant stress). They can also be used as noise and vibration absorbers and heat interchangers, as a basis for catalisers, etc.

Manufacture of closed-pore metal foams is almost exclusively centred on aluminium foams, while other alloys need to be researched and developed further (steel, copper, etc). There are a number of manufacturing processes and, using one or another method, sheets of foam material or complex shapes can be obtained.

Sheet material is used in a number of applications: reducing noise on roads and bridges, fire protection in buildings, impact-resisting structures for automobiles, etc. A second method enables the manufacture of complex shapes of metal foam with a solid external ’skin’. This enables the production of an endless array of applications with complex geometrical shapes. An example of the application of sandwich-type parts is in the majority of impact-resisting structures used in automobiles for improved passive safety (crash-boxes, doors, roofs), as well as ultralight structures.

Unlike closed-pore metal foams, the manufacture of open-pore foams is mainly based on the use of filler material and polymeric moulds the shapes of which are reproduced in metal, with the subsequent elimination of the mould. These types of structures can be made in almost any type of metal (Al, Cu, Mg, Fe, steel, etc.), both by casting and by processes of pulvimetallurgy, chemical deposition, etc.

In conclusion, metal foams can be seen as a future technology with high growth prospects in industrial use in the short- and medium term, given that they respond perfectly to the exigencies from a variety of markets: reducing weight in structures, safety in transport, noise reduction, yield enhancement in industrial processes, etc. All this at a competitive cost, which contributes substantially to business efficiency and competitiveness.

Contact :
Haridian Cubillo Oliva
INASMET
hcubillo@inasmet.es
(+34) 943 003700