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

Bing Chen; Suzhi Li; Hongxiang Zong; Xiangdong Ding; Jun Sun; Evan Ma

doi:10.1073/pnas.1919136117

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

Proc Natl Acad Sci U S A. 2020 Jul 14;117(28):16199-16206. doi: 10.1073/pnas.1919136117. Epub 2020 Jun 29.

Authors

Bing Chen¹, Suzhi Li², Hongxiang Zong¹, Xiangdong Ding¹, Jun Sun¹, Evan Ma³

Affiliations

¹ State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, China.
² State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, China; lisuzhi@xjtu.edu.cn ema@jhu.edu.
³ Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD 21218 lisuzhi@xjtu.edu.cn ema@jhu.edu.

Abstract

Atomistic simulations of dislocation mobility reveal that body-centered cubic (BCC) high-entropy alloys (HEAs) are distinctly different from traditional BCC metals. HEAs are concentrated solutions in which composition fluctuation is almost inevitable. The resultant inhomogeneities, while locally promoting kink nucleation 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 activated process of nanoscale segment detrapping, with comparable activation barrier. As a result, the mobility of edge dislocations, and hence their contribution to strength, becomes comparable to screw dislocations.

Keywords: BCC high-entropy alloys; dislocation mobility; local composition; solid-solution trapping.