Dislocation core structures and Peierls stresses of the high-entropy alloy NiCoFeCrMn and its subsystems

Abstract

High entropy alloys (HEAs) have emerged as promising next-generation structural materials. In order to understand the strengthening mechanism in these multicomponent alloys, a theoretical investigation is presented here in the framework of the Peierls-Nabarro (PN) model, which we consider would be appropriate for FCC HEAs due to their homogeneous feature, small lattice distortions and wide dislocation core structures. More importantly, there is no need to differentiate solutes and solvents in this model, which avoids the conceptual difficulties for such alloys. Using PN model, we calculate the dislocation core structures and Peierls stresses of the prototypical NiCoFeCrMn HEA and its six subsystems using the averaged gamma surfaces. The calculated stacking fault widths are in good agreement with available experimental data, and the obtained core structures are important for the future evaluation of the solute-dislocation interaction energies. The Peierls stresses in these multicomponent alloys are found to be much larger than pure FCC metals, and are generally in the same order of magnitude as the critical resolved shear stresses (CRSSs) extrapolated to zero temperature. The results indicate that in contrast to conventional FCC metals, the increased Peierls stresses in MEAs and HEAs could be responsible for their high yield stresses.