High strength and ductility in a lightweight AlTiNbZrTa refractory high-entropy alloy enabled by nanophase precipitation and solute segregation

A lightweight body-centered-cubic (BCC) AlTiNbZrTa refractory high-entropy alloy (RHEA) was developed, exhibiting an exceptional combination of high tensile strength (∼1,140 MPa) and ductility (∼30.2% elongation) after a tailored thermomechanical treatment (TMT). This TMT process resulted in significant microstructural refinement, including grain-size reduction, a high density of dislocations, and crucially, the formation of homogeneously distributed B2 and Zr₅Al₃-type nanophases. These nanophases are a direct consequence of solute segregation to dislocations during cold rolling, followed by precipitation during a subsequent heat treatment. The good mechanical properties of this RHEA are attributed to the combined effects of solid-solution strengthening, grain-boundary strengthening, dislocation strengthening, and precipitation hardening. Interestingly, solute segregation along dislocations is observed after cold rolling, resulting in the formation of B2 and Zr₅Al₃-type phases during the post-rolling heat treatment. In summary, this lightweight RHEA demonstrates significant potential for high-performance structural applications.