Freiberg University: Tapping into magnesium for lightweight construction

It is lighter than aluminum. Nevertheless, magnesium has hardly been used by industry to date, as its processing into components is considered complex and energy-intensive. After three years of research, a team from various departments at TU Bergakademie Freiberg, together with industry partners, developed and tested a continuous process chain for lightweight magnesium components. Energy consumption and CO₂ emissions were reduced across all process steps – among other things through the use of hydrogen in melting and heating technology, shortened processes, and a cold-formable magnesium alloy. The research consortium has produced, among other things, lightweight magnesium computer cases, rear seat backs for high-speed trains such as the TGV, hinge parts for transport containers, and an air duct for a hovercraft rescue vehicle.

Starting with sheet metal production, the team at the Institute for Metal Forming at TUBAF is focusing on innovative processes: "The casting rollers used already enable the production of magnesium sheets with thicknesses of around five millimeters. This reduces the number of downstream forming steps," says Professor Ulrich Prahl from the Institute for Metal Forming atTUBAF. The result is magnesium components that are around a third lighter than common aluminum solutions while offering comparable strength. This will allow the potential of magnesium as a lightweight material to be better exploited in the future – for example, in e-mobility, mechanical and vehicle engineering, and medical technology.

• Three building blocks for more efficient and climate-friendly magnesium processing

As the first component of the new manufacturing process, the researchers developed technologies that can replace fossil fuels with up to 100 percent climate-neutral hydrogen. "Converting the melting and heating processes to hydrogen and making them energy-efficient is a key step toward producing magnesium in a climate-neutral and more cost-effective manner in the future," says Professor Hartmut Krause from the Chair of Gas and Thermal Engineering at TUBAF . "Digital twins help us to better understand the processes and, above all, to improve them in operation.".

A second lever lies in the significantly shortened process route. For the rapid conversion of the liquid magnesium melt into a preliminary product, the team relies on the cast rolling process integrated at the Institute for Metal Forming. In this process, the heat from the casting heat is used directly for forming, resulting in sheets or wires that already have almost the desired component shape. This reduces energy- and time-consuming downstream process steps.

For wire production, the research team also developed the GieWaCon process, which combines wire casting and rolling with the CONFORM™ process. The latter is already established for materials such as copper and was transferred to magnesium for the first time in this project. Since the CONFORM™ process operates at room temperature, the heat generated during the casting process can be used to produce a wire product directly in just a few process steps. The magnesium wires produced in the project achieved a final diameter of 1.6 millimeters – either directly using the CONFORM™ process or by subsequent wire drawing.

In addition, the project shows that the principle of the shortened process route can also be transferred to other forming processes. For example, the magnesium alloy used was successfully forged; the resulting components were reworked immediately after forming, for example by deburring or milling. In addition, an industrial partner developed an extrusion process in which bolts are first cast and then extruded while still hot from the casting process. The resulting tube is cut open and bent so that workable sheets can be produced – also without additional heating steps.

The third component is the calcium-containing magnesium alloy ZAX210. It can be processed well at comparatively low forming temperatures of around 200 °C, while still ensuring stable mechanical properties. "The magnesium alloy allows us to carry out forming processes at significantly lower temperatures without compromising component properties," explains Professor Ulrich Prahl.

In addition, suitable surface coatings were investigated for all prototypes to ensure the corrosion resistance and usability of the magnesium components under real-world conditions. The project team also analyzed and optimized various welding processes, which were specifically adapted to the magnesium alloy used and further developed for the respective demonstrators.

Together with the industry partners involved in the project, the team intends to continue advancing the manufacturing routes developed and apply them to other components and forming processes in the future. A CO₂ calculator that companies can use to compile and compare possible process chains for magnesium forming has been developed specifically for this purpose as part of the project – the CLEAN-Mag app.