Rhenium alloying strengthens a ductile refractory high entropy alloy

Strengthening alloys at both ambient and elevated temperatures without compromising room temperature ductility remains a significant challenge in the structural materials field. Recently, we reported a ductile NbTaTi-based refractory high-entropy alloy (RHEA) capable of maintaining high strength up to 1200°C. In this study, we demonstrate that adding 1 at. % Re to this alloy provides further strengthening while preserving excellent cold machinability. Additionally, microstructure optimization was achieved through partial recrystallization, resulting in a heterogeneous lamella structure with alternating coarse and fine grain layers. This optimized structure further enhances the alloy's room temperature tensile strength, exceeding 1 GPa with uniform elongation above 10%. The designed alloy also retains a high strength of nearly 150 MPa at 1300°C. Our findings demonstrate that Re alloying is an effective strategy for improving the mechanical properties of NbTaTi-based RHEAs.