Grain refinement induced dynamic plasticity improvement in lightweight high entropy alloys

Lightweight high-entropy alloys (LHEAs) have gained significant attention due to their exceptional mechanical properties. Understanding the mechanical properties and microstructural evolution of LHEAs under dynamic loading is crucial for their development and utilization. Current studies have shown that severe local deformation occurs during dynamic deformation, leading to dynamic instability and low ductility. This work investigates the mechanical behavior of the non-equimolar Ti-Zr-Nb-based LHEA at high strain rates (2.8×10³ s^-1 - 4.5×10³ s^-1) by varying the grain size. The results indicate that grain refinement enhances the dynamic fracture ductility of LHEAs from ∼34% to ∼44%. The study of deformation microstructure reveals that grain refinement significantly increases the density of dislocations, promoting more regions to participate in deformation, and enhancing the interaction between dislocations, resulting in improved strain hardening ability (from negative to positive) and ultimately achieving a significant improvement in uniform deformation capability. These findings offer valuable insights into optimizing the strength and plasticity of LHEAs and other alloy systems under dynamic loading.