Research on the Constitutive Relationship and Mechanical-Chemical Coupling Effects of Novel Refractory High-Entropy Alloys

To overcome the brittleness of the W-Zr binary alloy system under ballistic conditions, a novel Nb₁₅Zr₃₅Ti₁₅W₃₅ refractory high-entropy alloy was designed and synthesized via vacuum arc melting with Ti and Nb additions. The microstructure, quasi-static/dynamic mechanical responses, constitutive relations, and energy release characteristics of the alloy were systematically examined to elucidate its mechanical-chemical coupling behavior under impact loading. The results indicate that the original brittle W₂Zr phase is replaced by W/TiₓW_y and Nbₓ/TiₓZr_y BCC solid solution phases; the dual-phase structure contributes to a notable positive strain rate effect. The critical fracture strain initially increases and then decreases with increasing strain rate, accompanied by significantly differentiated energy release behavior across strain rates. When the strain rate exceeds 3135 s⁻¹, shear-induced cracks and localized reactions occur, with an optimal balance of strength, plasticity, and chemical reactivity observed within the 3135~3931 s⁻¹ range. A modified Johnson-Cook model accurately captures the thermo-mechanical and dynamic flow behavior of the alloy. During impact compression, significant slip occurs along the direction of maximum shear stress, ultimately leading to fracture. Ti and Zr are identified as the primary reactive elements participating in oxidation with air, and the presence of solidified molten droplets on fracture surfaces confirms the alloy’s considerable plasticity.