Unveiling the dynamic mechanical behavior with phase-transformation and microstructural evolution in a novel dual-phase high-entropy alloy

A novel TiZrHfTaMo refractory high-entropy alloy (RHEA) was developed by adding Molybdenum to the TiZrHfTa system to enhance its mechanical properties. This study investigates the alloy's microstructural evolution and mechanical behavior under quasi-static (1.0 × 10⁻³ s⁻¹) and high-strain-rate compression following a specifically designed multi-stage heat-treatment. The heat-treated alloy exhibited a quasi-static-compressive yield-strength (YS) of ∼1,100 MPa and an ultimate-compressive-strength of ∼1,367 MPa. Under dynamic-loading, the YS significantly increased by ∼72.73 % to ∼1,900 MPa at a strain-rate of 3.0 × 103 s⁻¹. This substantial enhancement in the strength is attributed to the material's high strain-rate-sensitivity (SRS) and considerable microstructural refinement. Microstructural characterization (X-ray diffraction, electron-backscatter diffraction, and transmission-electron microscope) confirmed a dual-phase [body-centered-cubic (BCC) and face-centered-cubic (FCC)] constitution. It was observed that the FCC phase stabilized during heat-treatment, while the BCC phase underwent dynamic-recrystallization during high-strain-rate compression. These nanoscale structural changes promoted phase-boundary interactions and impeded dislocation motion, thereby improving overall mechanical stability. Furthermore, the SRS analysis revealed that the SRS exponents increased with respect to strain-rate, reflecting enhanced dislocation dynamics and strain-hardening mechanisms. In summary, this TiZrHfTaMo RHEA demonstrates excellent strength, stability, and adaptability across different loading conditions, positioning it as a promising candidate for structural applications.