The dual role of short-range order: A critical temperature switch between strengthening and weakening in high-entropy alloys

Short-range order (SRO) structures have recently attracted significant attention as an effective strategy for tailoring the mechanical properties of high-entropy alloys (HEAs). However, the underlying mechanisms governing the interactions between SRO structures and dislocation interactions remain inadequately elucidated. In this study, we systematically investigate the influence of SRO structure on the deformation behavior of the FeNiCrCo HEAs under shear loading using a hybrid Monte Carlo/molecular dynamics simulation method. The results demonstrate that the critical resolved shear stress (CRSS) of the HEAs decreases with increasing temperature, regardless of whether the alloys contain SRO structures. Notably, a critical transition temperature is identified: above this threshold, the SRO structures can enhance the CRSS, whereas below it, they diminish the CRSS. Further analysis reveals that the CRSS of the SRO_HEA is governed by a combination of solid solution strengthening from the matrix and additional strengthening induced by the SRO within Cr-rich region. In contrast, the CRSS of the RSS_HEA depends solely on solid solution strengthening. The temperature dependence of the CRSS in the SRO_HEAs is primarily attributed to the varying contributions of these two strengthening mechanisms with temperature. Moreover, as the degree of SRO increases, the lattice distortion in the matrix attenuates, the area of Cr-rich regions on the dislocation slip plane expands, and phonon scattering decreases—all factors facilitating dislocation motion. These findings provide fundamental insights into the microstructure design of the HEAs based on SRO engineering.