Mechanical response and deformation behavior of Al 0.6 CoCrFeNi high-entropy alloys upon dynamic loading

The mechanical properties and microstructure evolution of dual-phase Al0.6CoCrFeNi high-entropy alloys (HEAs) upon dynamic loading are investigated. Dynamic impact tests with varying strain rates of 2800–4000 s−1 at room temperature are performed by the split-Hopkinson pressure bar (SHPB). The yielding strengths evidently increase with increasing the strain rate for the present system. The high strain-rate sensitivity (SRS) parameter is extracted from the observed stress-strain responses. A modified Johnson-Cook (J-C) plasticity constitutive model is proposed to characterize the dynamic flow behavior. Nanoscale deformation twins induced by dynamic loading, accompanied by high density dislocation substructures, realize the excellent strength-ductility combination. According to the critical stress theory, the stacking fault energy (SFE) of the FCC phase can be estimated to be about 36 mJ/m2, which is evidently lower than the overall SFE for the Al0.6CoCrFeNi HEA.