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

B Chen and SZ Li and HX Zong and XD Ding and J Sun and EA Ma, PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 117, 16199-16206 (2020).

DOI: 10.1073/pnas.1919136117

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.

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