The Engineering Structures Laboratory of the Swiss Federal Laboratories for Materials Science and Technology (EMPA), Switzerland, has reportedly developed an iron-based shape-memory alloy for reinforcing concrete that has a lower melting point and is lower in cost than nickel-titanium SMAs. The iron-manganese-silicon alloy is activated at just 160°C, a temperature much more suitable for concrete than SMAs activated at 400°C. Researchers designed a range of virtual alloys based on thermodynamic simulations, and then selected the most promising combinations.
These were then manufactured in the laboratory and their shape memory characteristics tested. Several of the new materials met construction engineers’ requirements, an important milestone on the path to providing economical shape-memory steel alloys for industrial applications – in other words, manufacturing them by the ton.
SMA materials have a promising future in the building industry since the process of pre-stressing is simpler and therefore cheaper than conventional techniques. In addition, they may allow engineers to create pre-stressed structures that are impossible or very difficult to achieve by conventional techniques. These include the use of short-fiber-reinforced concrete, near-surface-mounted laminates, column wrapping, and ribbed armoring steel.
A feasibility study financed by the Swiss Commission for Technology and Innovation recently showed that it is possible to produce the new alloys on an industrial scale. The manufacturing process has been developed in collaboration with Leoben University (Austria), the Technical University Bergakademie Freiberg (Germany), and the German company G. Rau GmbH.
The working of cast ingots, each about 100 kg in weight, into thin strips around 2 mm thick, or ribbed armoring steel rods at temperatures over 1000°C, requires a high degree of technical knowledge, and the appropriate infrastructure. The process also needs to be adapted for the novel alloys.
The cost of the new products is expected to be about the same order of magnitude as that for stainless steel-based materials.
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