Effect of Stacking Fault Energy on the Dynamic Mechanical Properties and Deformation Mechanisms of CrMnFeCoNi High-Entropy Alloys

CrMnFeCoNi high-entropy alloys (HEAs) have attracted considerable attention because of their excellent mechanical properties. Furthermore, these alloys exhibit high energy absorption characteristics under high-strain rate deformation for various deformation modes. The stacking fault energy (SFE) plays a crucial role in improving the deformation modes and mechanical properties. Only few studies have investigated the effect of SFE on the dynamic mechanical properties and deformation mode of CrMnFeCoNi series HEAs. In this work, the effect of SFE on the dynamic mechanical properties and deformation mechanism of CrMnFeCoNi HEAs were investigated through quasi-static and dynamic mechanical tests and microstructural analysis using CrMnFeCoNi (SFE of 35 mJ/m²) and Cr 26^Mn20 Fe₂₀Co 20^Ni14 (SFE of 23 mJ/m²) HEAs. Results indicate that CrMnFeCoNi and Cr 26^Mn20 Fe₂₀Co 20^Ni14 HEAs exhibit a strain-rate hardening effect under dynamic deformation. Furthermore, the flow stress, energy absorption ability, and work hardening index increase under static and dynamic conditions with the decrease in SFE. Under quasi-static compression, deformation occurs via dislocation gliding in CrMnFeCoNi, whereas deformation twinning is profound in Cr₂₆Mn₂₀Fe₂₀Co₂₀Ni₁₄HEA with low SFE; therefore, deformation is dominated by dislocation slip and twinning. The contribution of deformation twinning to the deformation strain increases with the increase in strain rates. In particular, deformation occurs via dislocation gliding and twinning in CrMnFeCoNi HEA. Apart from dislocation slip and twinning, the interaction of twins and the transition from fcc to hcp structures provide additional deformation modes to accommodate the plastic deformation of Cr₂₆Mn₂₀Fe₂₀Co₂₀Ni₁₄HEA and improve the mechanical properties and energy absorption of these alloys. This work demonstrates that the change in SFE will lead to different deformation modes for accommodating plastic strain, thereby improving the mechanical properties of HEAs.