## 4 Conclusions  
The impact of tungsten on Laves phase precipitation during thermomechanical treatment and on the corresponding strengthening effect in two newly designed fully ferritic model alloys was investigated. The thermomechanical treatments were performed using a thermomechanical treatment simulator (TTS). The investigations of the strengthening effect were performed at ambient temperature. Due to the aim of high-temperature application, the presented results should serve as a base for pursuing the high temperature characterization and further development of this class of steels. The following conclusions can be drawn:  
* A fine and homogeneous thermomechanically induced precipitation of the Laves phase in fully ferritic steels is possible and can be controlled by the selection of the deformation parameters. The targeted and fast precipitation within a few minutes during thermomechanical treatment could replace the conventional two-step tempering treatment to precipitate the Laves phase, which takes several hours. As a result, the integrated thermomechanical process opens up a new, more effective, and more economical processing route for high-performance ferritic (HiperFer) stainless steels.
* Tungsten, as the main Laves phase-forming element, is necessary for the desired Laves phase precipitation. In both investigated model alloys with respective tungsten contents of 2.6 wt. % (Fe17 Cr2.6W) and 3.6 wt. %(Fe17 Cr3.6W), the precipitation of the fine and homogeneous dispersed strengthening Laves phase was achieved. Corresponding to the precipitation strengthening, an increase in yield and ultimate tensile strength of approximately 200 MPa was achieved in comparison to the particle-free, undeformed state. The 1 wt. % higher tungsten content in the  
Figure 9: Tensile test results of model alloys Fe17 Cr2.6W and Fe17 Cr3.6W after the newly developed thermomechanical processing chain in comparison to an undeformed, precipitate-free state.  
Fe17 Cr3.6W alloy results in approximately 30 MPa higher strength values caused by the higher phase fraction of the Laves phase.
* The amount of expensive tungsten is directly related to the total production costs of the alloy. Corresponding to the results, 2.6 wt. % of tungsten is sufficiently beneficial for the desired strengthening effect at ambient temperature. Moreover, a further increase to 3.6 wt.% did not cause significant progress in yield strength or in ultimate tensile strength.  
Conceptualization, J.P. and W.B.; methodology, B.K. and W.B.; investigation, J.P. and X.F.; data curation, J.P. and X.F.; writing--original draft preparation, J.P.; writing--review and editing, B.K., W.B. and U.K.; visualization, J.P.; supervision, W.B. and U.K.; project administration, J.P., W.B. and B.K. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
The investigations were financially supported by Deutsche Forschungsgemeinschaft (DFG). The authors gratefully acknowledge the support of the staff at the Steel Institute IEHK at RWTH Aachen University and at the Institute of Energy and Climate Research (IEK), Microstructure and Properties of Materials (IEK-2), Forschungszentrum Julich GmbH in performing the deformation experiments, microstructural investigations and mechanical tests.  
The authors declare no conflict of interest.