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Natural-mixing guided design of refractory high-entropy alloys with as-cast tensile ductility

Abstract

Metallic alloys containing multiple principal alloying elements have created a growing interest in exploring the property limits of metals and understanding the underlying physical mechanisms. Refractory high-entropy alloys have drawn particular attention due to their high melting points and excellent softening resistance, which are the two key requirements for high-temperature applications. Their compositional space is immense even after considering cost and recyclability restrictions, providing abundant design opportunities. However, refractory high-entropy alloys often exhibit apparent brittleness and oxidation susceptibility, which remain important challenges for their processing and application. Here, utilizing natural-mixing characteristics among refractory elements, we designed a Ti38V15Nb23Hf24 refractory high-entropy alloy that exhibits >20% tensile ductility in the as-cast state, and physicochemical stability at high temperatures. Exploring the underlying deformation mechanisms across multiple length scales, we observe that a rare β′-phase plays an intriguing role in the mechanical response of this alloy. These results reveal the effectiveness of natural-mixing tendencies in expediting high-entropy alloy discovery.

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Fig. 1: The strategy of composition search among refractory elements.
Fig. 2: Mechanical behaviour of the designed Ti38V15Nb23Hf24 RHEA and its equiatomic variant.
Fig. 3: Investigation of deformation mechanisms for the Ti38V15Nb23Hf24 RHEA at the mesoscale.
Fig. 4: Atomic-scale characterization of structural heterogeneity within the Ti38V15Nb23Hf24 RHEA.

Data availability

The datasets generated during the current study are available from the corresponding author on request.

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Acknowledgements

The TEM analyses were accomplished at the Materials Research Science and Engineering Center (MRSEC) shared experimental facilities at the Massachusetts Institute of Technology, financially supported by the National Science Foundation (NSF) under grant no. DMR-1419809. The synchrotron X-ray diffraction experiments were carried out on beamline 11ID-C at the Argon National Laboratory, Chicago, US (with the assistance of P. Gao and Y. Ren). S.J.K. and E.S.P. acknowledge financial support from the Creative Materials Discovery Program through the National Research Foundation (NRF) funded by the Ministry of Science and ICT, Korea (no. NRF-2019M3D1A1079215) and the Institute of Engineering Research at Seoul National University. T.F. acknowledges financial support from JSPS KAKENHI under grant no. JP18H05456 (Grant-in-Aid for Scientific Research on Innovative Areas 2018-2023). Y.J.Z. and T.F. thank K. Shinbo for technical support on APT measurement and G. Miyamoto for valuable discussions. S.L.W. and C.C.T. thank J. Li, D. B. Miracle, H. Oh, F. He, J. Kim, S.-S. Rui and M. Kim for their contributions.

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S.L.W. and C.C.T. conceptualized the project and designed the research; S.L.W. was the leading research scientist of this work; S.L.W., S.J.K. and E.S.P. fabricated the RHEA ingots; S.L.W. and S.J.K. conducted the thermodynamic computations; J.Y.K. and S.L.W. performed the in situ synchrotron X-ray diffraction experiments; S.L.W. and Y.Z. carried out the TEM characterizations; Y.J.Z. and T.F. performed the APT measurements; S.L.W. and C.C.T. analysed the data and wrote the paper and the supplementary information; and all authors discussed the results and approved the final version of the manuscript.

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Correspondence to Cemal Cem Tasan.

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Supplementary Figs. 1–17, Tables 1–3, Notes 1–4 and references.

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Wei, S., Kim, S.J., Kang, J. et al. Natural-mixing guided design of refractory high-entropy alloys with as-cast tensile ductility. Nat. Mater. 19, 1175–1181 (2020). https://doi.org/10.1038/s41563-020-0750-4

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