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

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 degrees C. Herein, a novel refractory Nb30Mo30Ti20Co20 (at. %) high-entropy superalloy (RHESA) is introduced. Annealing at 1200 degrees 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 degrees C.

Automated summary

This study introduces a new refractory high-entropy superalloy RHESA, which shows improved application prospects at high temperatures by balancing the mechanical properties of various nanoprecipitates. The emergence of multi-type nanoprecipitates in the RHESA enhances the room-temperature compressive ductility without compromising the material strength, addressing a major issue of low stability of B2 dispersoids in current RHESAs at temperatures above 700 degrees Celsius.