Achieving dynamic strength-plasticity synergy in refractory eutectic high-entropy alloy via nanolaminate-mediated R-phase transformation

Refractory high-entropy alloys (RHEAs) exhibit high strength but often possess poor castability and limited plasticity, especially under dynamic loading, which severely restricts their potential for impact-related applications. This study reports exceptional dynamic mechanical properties in a Ti₂ZrNbNi₃ refractory eutectic high-entropy alloy (R‑EHEA). The alloy, featuring an ultrafine lamellar microstructure of BCC and B2 phases, achieves a compressive strength of 2083 ± 36 MPa with 19.7 ± 0.8% plastic strain at ∼3000 s⁻¹, surpassing most reported RHEAs and eutectic HEAs. Crucially, it demonstrates an anomalous strain‑rate sensitivity where both strength and plasticity increase concurrently. Microstructural analysis reveals that this unique behavior stems from a deformation mechanism shift: under dynamic loading, a B2 → R‑phase transformation dominates, replacing the dislocation‑mediated B2 → B19′ transformation observed quasi‑statically. This transformation, facilitated by short‑range atomic displacements, generates nanosized, multi‑variant R‑phase precipitates. High-density interface generated by the R-phase transformation acts as a strong obstacle, restricting the long-range movement of dislocations, while forcing dislocations to store/reorganize at the interface, contributing to work hardening and plasticity. Additionally, the strain coordination during the phase transformation process itself is an additional source of plasticity. These results elucidate the mechanistic origin of superior dynamic strength‑plasticity synergy in RHEAs, providing a new paradigm for designing refractory alloys for dynamic applications. © 2026 The Author(s).