Light and Airy Metals

The automotive and construction engineering industries are increasingly benefiting from the low weight of foamed metals. The first series-produced machine tools have mechanical properties superior to those of their solid metal counterparts.

The development of foamed metals may have taken its inspiration from wood and bones. The cellular structure of trees, like that of human and animal skeletons, has the effect of reducing weight while maintaining a high level of tensile and breaking strength. Structuring metals in a controlled way poses a real challenge to material researchers: How can gas be introduced into metals so that they become as porous as a sponge? Metal powders are mixed with small quantities of sponging agents and pressed into strands with varying profiles. A second way of producing components close to their ultimate shape is to fill hollow steel bodies with compacted semi-finished material. When heated up, hydrides produce hydrogen and carbonates carbon dioxide. The knack is to find the right balance between the metal and the sponging agent, since the foaming effect must set in at just under the metal’s melting point. At the same time, a certain time-temperature profile should be kept so that the product will form the desired porous structure without collapsing later on.

A leading light in the production of lightweight metals is the Metal Foam Center in Chemnitz, initiator of the “Association for Cellular Materials Saxony”. Founded in 1998 as a special laboratory of the Fraunhofer Institute for Machine Tools and Forming Technology IWU, the Center has meanwhile accumulated an huge collection of different furnaces, processing machines and analysis tools. “We are able to offer our customers end-to-end service,” insists the Center’s director Thomas Hipke. “We cover everything from the project idea, the initial draft, design and computer simulation, through to the manufacture of the component.” Cross-institute collaboration enables the researchers to monitor whether the desired properties have actually been obtained. The Association is among the exhibitors at the Hanover trade fair in the “Innovation Center for Engineering Materials” in Hall 5.

The success of this work is manifested in numerous prototypes and initial serial components – particularly in the field of mechanical engineering. Depending on the industrial requirements, the new components come in many different variations: foam-filled carrier structures and differently welded sandwich constructions made of steel plates with aluminum foam between them. What all these models have in common is a significant weight reduction and enhanced mechanical damping during operation. The world’s largest foamed metal component is six meters long, and was designed and manufactured for a tooling machine named Dynapod.

http://www.fraunhofer.de/

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