In order to cope with the energy turnaround, the internal combustion engine powered by fossil fuels will be replaced by alternative drive concepts in passenger cars. For commercial vehicles, experts estimate that the diesel engine will continue to be used during a transition period or even longer when operated by synthetic fuels. In order to meet the increasing requirements in terms of durability, low fuel consumption and reduced emissions, the internal combustion engines must undergo continuous further development. From the materials point of view, the above-mentioned parameters are to be optimized by using aluminum-alloyed lightweight steels. Besides the decrease in density, alloying with aluminum increases the oxidation resistance of the steel, thus reducing fuel consumption and increasing the durability of engine components.

Since components in the powertrain of internal combustion engines are subjected not only to thermal but also to thermomechanical load, a key focus of the materials development carried out is to ensure adequate strength even at elevated operating temperatures. Precipitation hardening by means of intermetallic phases has particularly high potential since these phases are characterized by high-temperature stability and hardly coarsen even over long periods of use. It has been shown that steels with 6 wt.% Al experience a significant increase in strength, even at application temperatures of 500 °C, through the precipitation of the Laves phase by alloying with niobium (1.25 wt.%) in combination with tungsten (1.25 wt.%) or molybdenum (0.75 wt.%).

Characterization of the evolution of the Laves phase as a function of the heat treatment parameters was performed by X-ray diffraction, scanning and transmission electron microscopy, allowing to establish a relationship between chemical composition and precipitation of the Laves phase. The investigations carried out have contributed to a better understanding of the precipitation process in Al-alloyed steels, enabling a systematical design of process chains for different applications.