Novel As-Cast Ti-rich Refractory Complex Concentrated Alloys with Superior Tensile Properties

Refractory complex concentrated alloys (RCCAs) have drawn particular attention for their high yield strength and superior softening resistance at high temperatures. However, poor room-temperature ductility and high density remain the main challenges for their processing and applications. Here, using inherent material characteristics as the alloy-design principles, three novel single-phase body-centered cubic structured Ti 3 Zr 1.5 Nb (1− x ) Mo x VAl 0.25 ( x = 0.1, 0.3, 0.5, marked as Mo0.1, Mo0.3, and Mo0.5, respectively) RCCAs with promising tensile ductility and relatively low density below 6 g cm −3 were developed by tailoring the Mo concentration. The introduction of Mo elements with high shear modulus promotes lattice distortion, contributing to enhanced lattice friction stress and yield strength. The Mo0.3 and Mo0.5 alloys exhibit tensile yield strengths exceeding 1100 MPa and high fracture elongation of over 15% in the as-cast state. Labusch’s model revealed that solid-solution strengthening induced by atomic size and shear modulus mismatch contributes most significantly to yield strength. Deformation microstructure observations uncovered that the formation of the kink bands, dense-dislocation walls, and Taylor lattices are highly effective in enhancing strain-hardening capacity due to their high density of dislocation boundaries, enabling the alloys to maintain high strength while yet ensuring enough ductility. This study provides new insights into the development of strong and ductile RCCAs with single-phase structures.