Suppression of dynamic recovery via localized solute pinning for superior high-temperature strength in a lightweight refractory medium-entropy alloy

The deployment of lightweight refractory high- and medium-entropy alloys in next-generation aerospace systems is critically hindered by an inadequate understanding of their dynamic softening mechanisms at elevated temperatures. Herein, we report an approach to control dynamic recovery and recrystallization in a single-phase BCC Ti–Zr–V–Nb system, achieving a 24% increase in 800 °C tensile strength (from 236 MPa to 292 MPa) while retaining substantial high-temperature plasticity (29.7% fracture strain) and comparable room-temperature ductility (18.2%). This enhancement is achieved not by second-phase formation, but by establishing a sluggish diffusion environment to control microstructural evolution. A niobium-mediated change in atomic diffusivity actively promotes the rapid formation of localized solute atmospheres at defects during deformation, which in turn exerts a potent pinning force to suppress dynamic recovery. This mechanism is reflected by the apparent retardation of dynamic recrystallization processes, characterized by a significant increase in low-angle grain boundaries (LAGBs) and kernel average misorientation (KAM). Furthermore, atomic-scale observations using Cs-corrected STEM and APT provide direct structural indications for the physical origin of these pinning forces, driven by the profound segregation of Nb-rich clusters at defects. Systematic interrupted tests quantitatively confirm that this intense solute pinning acts continuously throughout the entire deformation process, severely restricting the recrystallization fraction and driving the continuous accumulation of an unrecovered substructure network. Our work establishes the targeted suppression of dynamic recovery through localized solute-defect interactions, providing a robust pathway for creating lightweight refractory alloys with superior high-temperature performance.