Metal foam

A metal foam, a porous foam made ​​of metallic materials is known. Metal foams are a focus of research in materials science.

Properties

Metal foams have a conditional through pores and cavities at low density but exhibit a high specific stiffness and strength. Usually of aluminum or aluminum alloys are expanded, since the starting materials already have a very low density. Using suitable propellants, it is also possible to prepare foams from copper, zinc, lead or iron / steel.

Production

Metal foams are often made by means of metal powder and a metal hydride, eg the Titandihydrid. Both powders are mixed together and compressed by hot pressing or extrusion of a starting material. The starting material is then heated to a temperature above the melting point of the metal. Here, the Titandihydrid sets gaseous hydrogen -free and foaming the mixture on.

There are other ways of producing metal foams. For example, to inject gas into molten metal, which has previously been made ​​foamable by the addition of solid components. For aluminum alloys are used for stabilizing 10-20 vol - added % silicon carbide or aluminum oxide. You can also add calcium. Here, forms an alloy. This increases the viscosity and stabilize the melt.

As a further process variant, the Schlickerreaktionsschaumsinter process is ( SRSS ) method available, with mainly iron, steel and nickel foams can be produced. In this method, a slurry is by means of hydrogen, which is formed by the reaction of the acid with the corresponding metal powder is foamed. With further reaction products, the foam structure is set and dried in a mold. The resulting green body is then sintered under a reducing atmosphere or in vacuum.

Application

Metallic foams exhibit good energy absorption capacity, and it is started to use aluminum foams as crash protection elements in the automotive industry. In the Audi Q7 aluminum foam crash absorbers are used in the luggage rack bracket to ensure occupant safety even in a deformed body. In the machine tool industry, metal foams are attractive for use in high dynamic stress machines. In particular, improved vibration damping in machine tools usually means a significant increase in production quality, which in turn usually reduces operating costs and increases productivity. Example here can be the universal slides of the machine tool Mikron HPM 1850 U call, which was developed in collaboration with the company Niles- Simmons industrial plants in Chemnitz and the Fraunhofer Institute for Machine Tools and Forming. The machine was first introduced to METAV 2004 and will be manufactured in series. Compared with the pure steel welded construction, the mass could be significantly reduced. Analogously improves the dynamic stiffness and damping characteristics. Other applications for metallic foams are heat shields, Wärmekapselungen, filters, catalyst supports, sound-absorbing panels or making very light, foam-filled rollers for the printing and paper industries.

In Finland, a barge to transport wood pellet made ​​of aluminum foam sandwich panels will ship built in 2011 for the first time.