Dynamic mechanical response and strain rate-microstructure coupled constitutive model of eutectic high-entropy alloys Ni30Co30Cr10Fe10Al18W2 by PSR and SPSR processes

This study prepared three Ni30Co30Cr10Fe10Al18W2 eutectic high-entropy alloys (EHEAs) in different thermomechanical states (one phase-selective recrystallization (PSR) state and two post-processing (SPSR) states), and systematically characterized their initial microstructural parameters to identify the key factors governing their mechanical properties. Quasi-static and dynamic tensile property tests were conducted on the three samples. The results show that in high strain rate tensile tests, the strength of the three alloys is significantly improved (the yield strength of the PSR alloy increases by 32.9%, and the ultimate tensile strength of the SPSR-2 alloy increases by 12.4%), while the failure strain decreases. Fractographic analysis reveals three distinct failure modes under dynamic loading: in the PSR state, cracks predominantly distribute along the FCC/B2 phase interfaces; in SPSR-1, cracks nucleate and localize within the BCC phase; in SPSR-2, cracks initiate in the BCC phase and then extend into the FCC phase, accompanied by secondary cracking. Based on these microstructural characteristics and considering strain rate effects, a dynamic constitutive model was established, uniquely integrating key microstructural parameters: grain size, interfacial spacing, and dislocation density. The model demonstrates excellent predictive accuracy across all three states, highlighting its generality beyond a single microstructure. This work not only deciphers the strengthening and failure mechanisms under impact loading but also provides a quantitative framework for tailoring thermomechanical processing to achieve targeted property combinations in EHEAs for specific applications.