Achieving high strength and high ductility in a high-entropy alloy by a combination of a heterogeneous grain structure and oxide-dispersion strengthening

Abstract Strengthening single-phase face-centered cubic high-entropy alloys (HEAs) by grain refinement is usually accompanied by a dramatic loss of ductility, which is referred to as the strength–ductility trade-off dilemma. To overcome this dilemma, we propose a strategy to achieve an excellent combination of high strength and high ductility by both designing a heterogeneous grain structure and dispersing oxide nanoparticles in the Ni2CoCrFeTi0.2 HEA. The alloy exhibited a high yield strength of up to 1070 MPa with an appreciable uniform elongation of 11.6%. Quantitative analysis indicated that grain-boundary strengthening, oxide-dispersion strengthening, and back stress strengthening are dominant strengthening mechanisms, while the good ductility was mainly attributed to back stress hardening and dislocation hardening. The present work provides deep insight for designing high-performance HEAs.