Influence of pre-deformation on the precipitation characteristics of aged non-equiatomic Co_1.5CrFeNi_1.5 high entropy alloys with Ti and Al additions

Non-equiatomic Co_1.5CrFeNi_1.5 high entropy alloys (HEAs) with Ti and Al additions (Al_0.5Co_1.5CrFeNi_1.5 – Al₀₅, Al_0.2Co_1.5CrFeNi_1.5Ti_0.3 – Al₀₂Ti₀₃ and Co_1.5CrFeNi_1.5Ti_0.5 – Ti₀₅), aged at 750 °C, exhibit pronounced precipitation hardening. The present work investigates the effect of pre-deformation on their aging response, primarily focusing on the precipitation characteristics and their effect on strengthening. Pre-deformation of 25% through quasi-static compression has been applied on the solution treated HEA samples. The pre-deformed samples have been aged at 750 °C for different time intervals. Interestingly, pre-deformed HEAs have shown reduced peak-aging time of 50 h in all the three HEAs, due to the enhanced precipitation kinetics arising from the significant increase in their dislocation densities. Microstructural investigations on the pre-deformed and aged alloys show distinct precipitate size and distribution characteristics. The same has been quantitatively assessed to understand their role on aging response and coarsening kinetics during over-aging.