Development and characterization of refractory high-entropy alloys for high temperature applications


Currently, Ni-based superalloys are the preferred materials for high-temperature gas turbine applications. However, their melting point of approximately 1450°C limits the temperature range in which they can be used, even with cooling and thermal insulation.

Refractory Compositionally Complex Alloys (RCCA) and Refractory High Entropy Alloys (RHEA) consist of a combination of mutually soluble refractory metals, typically resulting in a disordered or ordered body-centered cubic crystal structure. The latter is defined as forming a single-phase microstructure, while the former can exhibit a multi-phase microstructure. Some of these alloys have been shown to outperform Ni-based superalloys in certain key structural properties, such as high-temperature strength or density.


  • Conventional metallurgical production of equiatomic and non-equiatomic Ta-Mo-Cr-Ti-Al alloys with uniformly distributed microstructure

  • Stabilization of a single-phase, homogeneous solid solution or two-phase compositionally complex alloys by tailoring the composition and specific heat treatments

  • Determination of reproducible, characteristic values for evaluating mechanical properties regarding high-temperature applications

  • Understanding of the deformation behavior of single-phase and multi-phase alloys with varying ordering states



  • Evaluation of the alloy quality by O-/N-analysis for investigating the material purity and by wet chemical analysis for exactly determining the alloy composition

  • Thermal analysis and high-resolution atom probe tomography to determine and characterize phase transitions

  • Compression tests as well as hardness measurements on different length scales for determining mechanical properties

  • Investigation of the microstructure in the heat treated and the deformed condition by diffractometric and microscopic characterization methods


SPP 2006 "Compositionally Complex Alloys – High Entropy Alloys" by Deutsche Forschungsgemeinschaft