Unique precipitations in a novel refractory Nb-Mo-Ti-Co high-entropy superalloy

Abstract

Herein, a novel refractory Nb₃₀Mo₃₀Ti₂₀Co₂₀ (at. %) high-entropy superalloy (RHESA) is introduced. Annealing at 1200 °C led to the precipitation of a semi-coherent individual (Co, Ti)-rich B2, (Ti, O)-rich fcc (Ti-rich oxides), and hierarchical B2 + fcc nanoparticles in the (Nb, Mo)-rich RHESA bcc phase. B2 + fcc dispersoids were dominant, and they nucleated heterogeneously because of the coherency ensured by the Baker–Nutting orientation relationship. The emergence of multi-type nanoprecipitates doubled the room-temperature compressive ductility without sacrificing strength. Our study can solve a chief problem of current RHESAs—the low stability of B2 dispersoids at T > 700 °C.

GRAPHICAL ABSTRACT

IMPACT STATEMENT

Multi-type B2, fcc, and B2 + fcc nanoprecipitates balancing mechanical properties of the refractory Nb₃₀Mo₃₀Ti₂₀Co₂₀ high-entropy superalloy (RHESA) endow new prospects for application of RHESAs at T ≥ 1200 °C.

KEYWORDS:

• Refractory high-entropy superalloys
• hierarchical precipitates
• B2 phase
• Baker-Nutting orientation relationship
• mechanical properties

Acknowledgements

This work was carried out using the equipment of the Joint Research Center of Belgorod State National Research University «Technology and Materials». The authors also thank Dr A. Belyakov, Belgorod National Research University, for fruitful discussions and Dr D. Shaysultanov for aid in an alloy's ingot preparation.

Data availability statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Russian Science Foundation grant number 19-79-30066.