Understanding the dynamic deformation behavior of advanced alloys under high-velocity impact is crucial for the design of protective structures and aerospace components. Taylor impact experiments are conducted on three CoCrNi-based medium-entropy alloys (MEAs) with similar grain sizes, CoCrNi, \(\mathrm{(CoCrNi)}_{94}\textrm{Al}_{3}\textrm{Ti}_{3}\) , and \(\mathrm{(CoCrNi)}_{90}\textrm{Al}_{5}\textrm{Ti}_{5}\) . The addition of aluminum and titanium induces the formation of nano scale L \(1_2\) precipitates in MEA3, larger L \(1_2\) precipitates and micron-sized BCC phase in MEA5. While dislocation glide and stacking faults are the dominant deformation mechanisms for all alloys, deformation twinning is prominent in the precipitate-free CoCrNi, becomes rare in \(\mathrm{(CoCrNi)}_{94}\textrm{Al}_{3}\textrm{Ti}_{3}\) , and is completely suppressed in \(\mathrm{(CoCrNi)}_{90}\textrm{Al}_{5}\textrm{Ti}_{5}\) . Deformation twinning of as-cast \(\mathrm{(CoCrNi)}_{94}\textrm{Al}_{3}\textrm{Ti}_{3}\) is observed for the first time under various loading conditions. Impact-induced gradient structures along the impact direction are observed in both macroscopic sample profiles and underlying microstructures. FEM simulations successfully capture the experimentally observed plastic deformation, validating the constitutive model parameters. The precipitation-hardened CoCrNi-based MEAs exhibit a reduced characteristic time to reach the strain plateau compared to CoCrNi. These findings provide new insights for designing MEAs with tailored microstructures for enhanced high-strain-rate performance.
