Influence of lattice distortion on stacking fault energies of CoCrFeNi and Al-CoCrFeNi high entropy alloys

The stacking fault energy (SFE) plays an important role in the deformation mode selection and consequently the mechanical properties of high entropy alloys. In the present work, the SFEs of face-centered cubic (fcc) CoCrFeNi and Al0.57CoCrFeNi HEAs are calculated by using first-principles calculations. The influence of the local lattice distortion (LLD) on the SFE is explored. We show that the addition of Al to CoCrFeNi alloy increases the intrinsic SFE (ISFE, γisf) but decreases the unstable SFE (USFE, γusf) such that the energy barrier (γusf - γisf) for the ⟨112-⟩(111) slip decreases. The lattice distortion contributes significantly to the ISFE but has limited influence on the USFE, leading to decline of the slip energy barriers of both alloys. The ISFE and slip energy barrier differences between the two alloys are enhanced by the lattice distortion. Based on the calculated ISFE and slip energy barrier, the effects of Al alloying and lattice distortion on the mechanical properties of CoCrNiFe HEA are discussed. •Addition of Al to CoCrFeNi decreases energy barrier for ⟨112-⟩(111) slip.•Lattice distortion decreases slip energy barriers of CoCrFeNi and Al0.57CoCrFeNi.•Contribution of lattice distortion to stacking fault energy against lattice distortion is independent of composition.•Lattice distortion amplifies mechanical property differences between CoCrFeNi and Al0.57CoCrFeNi.