Exceptional ambient- and elevated-temperature mechanical performance of a cast multi-phase (Ti,Sc,Zr)66(Nb,V)34 lightweight compositionally complex alloy

The pursuit of lightweight structural materials with exceptional mechanical performance across a broad temperature spectrum remains a significant challenge for advanced engineering applications. This study addresses this challenge by introducing a cast (Ti,Sc,Zr) 66 (Nb,V) 34 lightweight refractory compositionally complex alloy (LRCCA) with a theoretical density of 5.4064 g cm −3 . The resulting multi-phase microstructure is characterized by phase-separated BCC dendrites, along with hypoperitectic interdendritic regions composed of equiaxed BCC grains and lamellar BCC/HCP duplex structures. This microstructural design utilizes the synergistic effects of its constituents to achieve an exceptional balance between strength and ductility under both ambient and elevated temperature conditions. At ambient temperature, the as-cast LRCCA demonstrates an ultimate tensile strength exceeding 1 GPa, a total elongation surpassing 10 %, and an impressive specific strength of ∼185.0 MPa cm 3 g −1 , primarily driven by the synergistic effects of dislocations, deformation twins, and additional HCP→FCC martensitic transformation. At 873 K, a pronounced ultimate tensile strength of approximately 649.5 MPa and an exceptional total elongation of ∼84.1 % are achieved, which arises from the synergistic interplay of limited dynamic recrystallization, dislocation motion, deformation twinning, and dual martensitic transformations (i.e., HCP→FCC and β →α″). This study indicates the critical role of microstructural engineering in optimizing the mechanical properties of CCAs, providing valuable insights for the development of next-generation lightweight materials.