Exploring hot _formability and strengthening mechanisms of a Co_39.2Ni_39.2Al_19.6Ti₂ dual-phase high entropy alloy

Dual-phase high entropy alloys demonstrate outstanding strength-ductility combination, however, the microstructure evolution during thermal processing and the strengthening mechanisms of the alloy after thermal processing still lack in-depth investigations. In this study, the dynamic recrystallization behaviors and microstructural evolution of the Co_39.2Ni_39.2Al_19.6Ti₂ dual-phase high entropy alloy were investigated over a temperature range from 950 ​°C to 1100 ​°C and a strain rate range from 1 s⁻¹ to 0.001 s⁻¹. The stress-strain curves have been accurately predicted using the Arrhenius constitutive equations, and the optimal thermal processing parameters was determined as 1050 ​°C/0.001 s⁻¹ through the established hot processing map. Characterization of the microstructure after thermal processing confirmed that microstructure obtained after optimal processing exhibited a high degree of dynamic recrystallization with no obvious texture. Further investigations revealed that in Co_39.2Ni_39.2Al_19.6Ti₂ dual-phase high entropy alloy, the dynamic recrystallization process of B2 phase was ahead of FCC phase under the same conditions, and three dynamic recrystallization mechanisms were found during the deformation process. After the optimal processing, the mechanical properties of the alloy showed great improvement, where the mechanical properties enhancement mechanisms arose from grain-refinement strengthening and the phase-interface strengthening. This study provides a comprehensive investigation into the thermoforming behavior and mechanical property optimization of dual-phase high entropy alloys.