Origin of age softening in the refractory high-entropy alloys

Liu, Junliang; Li, Bo-Shiuan; Gardner, Hazel; Gong, Yilun; Liu, Fengxian; He, Guanze; Moorehead, Michael; Parkin, Calvin; Couet, Adrien; Wilkinson, Angus J.; Armstrong, David E. J.

doi:10.1126/sciadv.adj1511

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Origin of age softening in the refractory high-entropy alloys

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Gong, Yilun
Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK;
Computational Materials Design, Max-Planck-Institut für Eisenforschung GmbH, Max Planck Society;

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Citation

Liu, J., Li, B.-S., Gardner, H., Gong, Y., Liu, F., He, G., et al. (2024). Origin of age softening in the refractory high-entropy alloys. Science Advances, 9(49): eadj1511. doi:10.1126/sciadv.adj1511.

Cite as: https://hdl.handle.net/21.11116/0000-000E-7FC9-2

Abstract

Refractory high-entropy alloys (RHEAs) are emerging materials with potential for use under extreme conditions. As a newly developed material system, a comprehensive understanding of their long-term stability under potential service temperatures remains to be established. This study examined a titanium-vanadium-niobium-tantalum alloy, a promising RHEA known for its superior high-temperature strength and room-temperature ductility. Using a combination of advanced analytical microscopies, Calculation of Phase Diagrams (CALPHAD) software, and nanoindentation, we investigated the evolution of its microstructure and mechanical properties upon aging at 700°C. Trace interstitials such as oxygen and nitrogen, initially contributing to solid solution strengthening, promote phase segregation during thermal aging. As a result of the depletion of solute interstitials within the metal matrix, a progressive softening is observed in the alloy as a function of aging time. This study, therefore, underscores the need for a better control of impurities in future development and application of RHEAs. Impurity elements were observed to induce softening in a newly designed TiVNbTa engineering alloy at high temperatures.