Development of New Advanced Refractory Concentrated Complex Alloys with Eutectic Carbide/BCC Microstructures – DoREMi

The DoREMI project offers to explore a new class of refractory complex concentrated alloys (RCCAs) with eutectic microstructures for structural applications in extreme temperature conditions. RCCAs are designed using a new alloying concept based on "high entropy" and the mixing of refractory elements in (near) equiatomic proportions. Those alloys generally have attractive mechanical properties but have been observed to lose their high-temperature strength above 1000°C. In the current project, we propose to add a massive quantity of carbon in RCCAs to trigger the formation of carbide-reinforced eutectic microstructure. The uniaxial mechanical properties of such eutectic alloys are much higher than the reported RCCAs. They support yield strength exceeding 1 GPa at 1200°C while keeping reasonable ductility at room temperature. However, the concept is new for those RCCAs with massive carbon addition, and it still needs to be rationalized, raising fundamental questions about thermal stability and underlying deformation mechanisms. These challenges require a multi-scale study from the alloy design to the study of the properties. Within this framework, a scientific approach is implemented and combines alloy design (based on thermodynamic calculations), alloy preparation (using classical and innovative routes), microstructure characterization and the analysis of macroscopic behavior and deformation micro-mechanisms using state- of-the-art experiments (in situ straining tests under a transmission electron microscope).