Jul 25 2006
To find a featherweight metal is every carmaker’s dream. Magnesium comes pretty close to this ideal. It weighs only about a third less than aluminum and is even two thirds lighter than steel – the perfect material, in fact, for building energy-saving cars. “But you can’t simply replace steel with magnesium,” states Michael Kieninger of the Fraunhofer Institute for Structural Durability and System Reliability LBF in Darmstadt. “However light they may be, the parts must still be capable of withstanding shock, vibration and corrosion – the car ultimately needs to be robust.”
Magnesium itself is too soft for use in vehicle construction, but its properties can be changed by combining it with other elements. Working with automobile manufacturers VW, Opel and Fiat in an EU project entitled “Mg-Chassis”, researchers from Germany, Sweden and Israel have developed and tested new magnesium alloys. The Magnesium Research Institute in Israel has created lightweight yet extremely robust materials from magnesium fused with small quantities of aluminum, zinc and manganese. Engineers at the Fraunhofer Institute for Manufacturing Engineering and Applied Materials Research IFAM in Bremen cast components from these materials. Scientists at the LBF put these demonstrators through their paces: “For the first time ever, we were able to examine all the relevant factors affecting the structural durability of components: resistance to vibration under loads with constant and variable amplitudes and fracture behavior on impact,” says Christian Pohl of the LBF. The researchers also examined the effect of lasting deformation on the life of the component, caused by factors such as the driver grazing the curb. “We found that many of the magnesium alloys possess excellent material properties and are suitable for safety-relevant components such as the chassis.”
A chassis made of magnesium alloys would be a real innovation: Until now, car manufacturers have used the lightweight metal almost exclusively for interior parts not important to the car’s safety, for instance as a dashboard support or instrument panel. The results of the EU project will greatly expand the range of potential applications for the super-light material, Christian Pohl believes: “Using our reference data, designers will now be able to determine the load-bearing capacity of a component, compare it with the actual loads incurred and then select the most suitable alloy.”