Unusual activated processes controlling dislocation motion in body-centered-cubic high-entropy alloys

Atomistic simulations of dislocation mobility reveal that body-centered cubic (BCC) high-entropy alloys (HEAs) are distinctly dif-ferent from traditional BCC metals. HEAs are concentrated solu-tions in which composition fluctuation is almost inevitable. The resultant inhomogeneities, while locally promoting kink nucle-ation on screw dislocations, trap them against propagation with an appreciable energy barrier, replacing kink nucleation as the rate-limiting mechanism. Edge dislocations encounter a similar ac-tivated process of nanoscale segment detrapping, with compara-ble activation barrier. As a result, the mobility of edge dislocations, and hence their contribution to strength, becomes comparable to screw dislocations.