Strain-Rate-Dependent mechanical behavior of a non-Equimolar CoCrFeMnNi high entropy alloy with a segmented coarse grain structure

The mechanical response of a Co11.3Cr20.4Fe22.6Mn21.8Ni23.9 (wt%) high entropy alloy with a segmented coarse grain structure is investigated using strain-rate-dependent uniaxial compression experiments. The composition is verified using ab-initio simulations by examining thermal stability through the reduction of Gibbs free energy relative to similar equi-molar alloys. The segmented grain structure, combining high-angle coarse-grains with low-angle sub-grains, provides good hardness (∼3 GPa) and strain-hardening (∼2600 MPa/ε). Yield strength shows strain-rate-dependent behavior with high strain-rate sensitivity. Here, the macroscopic deformation is correlated with the microscopic plastic failure mechanisms, facilitated by advanced in situ visualization and analysis. Results reveal that the formation of deformation bands occur before yield, while the interactions between microscopic plastic deformation mechanisms and the low-angle sub-grain boundaries significantly affect the apparent surface deformation features and mechanical properties.