Multi-scale microstructure to address strength-ductility trade-off in novel Ti-V-Al-Zr-Nb lightweight refractory complex concentrated alloys

• Synergistic optimization of strength and ductility in LRCCAs through hot rolling and annealing treatments. • Heterostructure-induced strain gradient and back stress strengthening mechanisms. • Nanoscale precipitates further enhance the multiscale heterostructure and mechanical properties. Lightweight refractory complex concentrated alloys (LRCCAs) exhibit remarkable advantages of high strength and low density. However, their inherent brittleness remains a key factor limiting their applications. This study found that hot rolling and annealing treatments can synergistically optimize the strength and ductility of the Ti 66.8 V 11.2 Al 9.6 Zr 6.2 Nb 6.2 LRCCA. After hot rolling and annealing, the LRCCA developed a heterogeneous grain structure consisting of “fibrous grains + equiaxed grains.” This heterogeneous structure promotes significant deformation inhomogeneity. Through these multi-scale coupling mechanisms, the alloy achieves a simultaneous improvement in both strength and ductility. Notably, the HRA580 alloy, annealed at a low temperature of 580 °C, precipitated nano-sized HCP phases. This resulted in a multi-scale heterogeneous structure of “fibrous grains + equiaxed grains + HCP precipitates”, while maintaining a high dislocation density. As a result, the alloy achieved an outstanding combination of ∼1400 MPa yield strength and ∼13 % fracture strain, along with a specific yield strength as high as 286 MPa·cm 3 /g. The coordinated deformation within the heterogeneous structure endows the alloy with exceptional mechanical properties. The findings of this study provide an important theoretical basis for advancing the application of LRCCAs in advanced manufacturing