Microstructure and mechanical properties of Ti3Zr1.5Nb(1-x)V(1+x)Al0.25 (x=0, 0.2, 0.4, 0.6, 0.8, and 1.0) refractory complex concentrated alloys

Refractory complex concentrated alloys (RCCAs) have garnered significant attention due to their exceptionally high yield strengths, yet their practical applications are severely limited by high density and inherent brittleness. This study seeks to develop novel RCCA systems with enhanced strength and ductility by strategically modulating Group VB elements. The synergistic effects of Nb and V on the as-cast microstructure and mechanical properties at both room and elevated temperatures of the Ti3Zr1.5Nb(1-x)V(1+x)Al0.25 (x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0) RCCAs were investigated in detail. Alloys with x <= 0.4 exhibit a single body-centered cubic (BCC) phase structure, while further V additions leads to the precipitation of a hexagonal ZrV2-type C14 Laves phase and even a V-enriched BCC phase in the interdendritic regions. With the increase in V concentration, the alloys display progressively enhanced strength. Notably, the Ti3Zr1.5Nb0.6V1.4Al0.25 alloy demonstrates optimal mechanical properties, achieving a tensile yield strength of similar to 1024 MPa, a plastic strain of similar to 12 % at room temperature, and a compression yield strength of similar to 689 MPa at 600 degree celsius. However, the precipitation of brittle phases along grain boundaries results in reduced plasticity in alloys with high V concentrations. The high yield strength of these alloys is primarily attributed to the intrinsic yield strength of the constituent elements, grain boundary strengthening, and solution strengthening induced by severe lattice distortion. This study offers a paradigm for understanding the impact of alloy composition on the structure and properties of RCCAs.