Theory-guided design of high-strength, high-melting point, ductile, low-density, single-phase BCC high entropy alloys

Theory-guided design of high-strength, high-melting point, ductile, low-density, single-phase BCC high entropy alloys

Description & AMAZEMET association

The search for new high-temperature alloys for efficient, low-emission power generation has led to breakthroughs in body-centered cubic (bcc) refractory High-Entropy Alloys (HEAs). In this study, advanced thermodynamic tools guided the discovery of HfMoNbTaTi and related quinary/quaternary alloys with exceptional strength, thermal stability, and ductility. Experimentally, a nominal alloy composition was arc-melted using pure metals and refined using the AMAZEMET rePowder 2 system, with rigorous processing ensuring homogeneity. The resulting single-phase alloy exhibited high hardness, a high melting point, and low density, showcasing the potential of this novel design methodology to explore millions of new alloys tailored to diverse performance demands.

Authors

Y. Rao ^a, ^*, C. Baruffi ^a , A. De Luca ^b, C. Leinenbach ^b , ^c , W.A. Curtin ^a

^a Laboratory for Multiscale Mechanics Modeling, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
^b Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland
^c Laboratory for Photonics Materials and Characterization, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland

^* Corresponding author: you.rao@epfl.ch (Y. Rao) .

Abstract

The search for new high-temperature alloys that can enable higher-efficiency/lower-emissions power gen- eration has accelerated with the discovery of body-centered cubic (bcc) refractory High Entropy Alloys (HEAs). These many-component, non-dilute alloys in the Cr-Mo-W-V-Nb-Ta-Ti-Zr-Hf-Al family hold the potential for combining high strength and thermodynamic stability at high temperature with low den- sity and room-temperature ductility, but searching the immense compositional space is daunting. Here, very recent theories and expanded thermodynamic tools are used to guide the discovery of new alloys satisfying the required suite of properties. The search and discovery method is first demonstrated for 5- component equicomposition alloys, identifying HfMoNbTaTi as the one alloy satisfying many constraints, with predicted properties agreeing with experiments. The design process then discovers new quinary and quarternary alloys in the Hf-Mo-Nb-Ta-Ti space having even better overall properties. One new quinary alloy is fabricated and shown to be single phase with high room temperature hardness, high melting point, and low density. More broadly, the new design process can further be used to explore millions of alloys with other desired multi-dimensional performance requirements.