Calphad-Guided Prediction and Interpretation of Phase Formation in Ta-Mo-Cr-Ti-Al Refractory High-Entropy Alloys

Strategic Insights -

Researchers at the Karlsruhe Institute of Technology (KIT) have conducted a study on designing alloys with a disordered body-centered-cubic (BCC) A2 crystal structure within the refractory high-entropy alloy (RHEA) system Ta-Mo-Cr-Ti-Al. The study utilized equilibrium calculations, microstructure analysis, and differential scanning calorimetry (DSC) to predict alloy compositions with a dominant disordered A2 phase, which is favorable for enhancing room-temperature ductility. The research also identified phase transitions taking place upon heating from room temperature to 1300 degrees C.

Key Takeaways:

  • Researchers designed alloys with a disordered BCC A2 crystal structure within the RHEA system Ta-Mo-Cr-Ti-Al using equilibrium calculations, microstructure analysis, and DSC.
  • The study aimed to enhance room-temperature ductility and reduced density and improved oxidation resistance in the alloy design.
  • DSC was used to identify phase transitions taking place upon heating from room temperature to 1300 degrees C.
  • Phase separation, ordering, and higher-order phase transitions were discussed in the results of microstructural characterization, X-ray diffraction, thermal analysis, and selected area electron diffraction by transmission electron microscopy.
  • The study has been peer-reviewed and published in the journal Advanced Engineering Materials in 2025.
  • The research team included Kateryna Khanchych, Chongchong Tang, Carsten Schroer, Björn Schäfer, Judith Jung, Michael Dürrschnabel, Ute Jäentsch, and Bronislava Gorr.
  • The study was funded by the Federal Ministry for Economic Affairs and Climate Action of Germany and the Helmholtz Association.

Statistics:

  • Time period: The study focused on designing alloys with specific properties and identified phase transitions taking place upon heating from room temperature to 1300 degrees C.
  • Temperature range: 1300 degrees C was the maximum temperature range considered in the study.
  • Phase transitions: Three types of phase transitions were identified: ordering, phase separation, and higher-order phase transition.
  • Alloy design: The study aimed to enhance room-temperature ductility and reduced density and improved oxidation resistance in the alloy design.
  • Research team: The team included 8 researchers from the Karlsruhe Institute of Technology (KIT).

Sources:

  • Calphad-guided Prediction and Interpretation of Phase Formation In Ta-mo-cr-ti-al Refractory High-entropy Alloys. Advanced Engineering Materials, 2025.
  • Findings on Engineering Reported by Investigators at Karlsruhe Institute of Technology (KIT) (Calphad-guided Prediction and Interpretation of Phase Formation In Ta-mo-cr-ti-al Refractory High-entropy Alloys). Journal of Engineering. June 16, 2025; p 1193.