Hydrogen induced dislocation core reconstruction in bcc tungsten

Dislocation, playing a crucial role in the plastic deformation of metals, can be significantly affected by introducing solute elements. Hydrogen (H) embrittlement is one such example, while the underlying mechanism for H affected dislocation structural stability and mobility remains unclear and the role of H has been controversial. Here, using first-principles calculations, we demonstrate that the effect of H on screw dislocation in bcc tungsten (W) is H concentration-dependent, signified by a H-induced tran-sition of SD core structure. At low concentrations of H segregation, dislocation maintains the intrinsic easy-core structure, and H atoms are attached to the periphery of dislocation to enhance dislocation motion. In contrast, at high H concentrations, dislocation transforms into a hard-core, metal hydride-like structure, as H atoms become the body of dislocation to significantly reduce the dislocation mobility in W. Further, such local easy-to-hard transition can also be induced by the other solutes, including he-lium, carbon, nitrogen and oxygen. Our work sheds new light on the H-dislocation interactions in bcc W, having broad implications in the interstitial solute-related phenomena.(c) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study uses first-principles calculations to reveal the effect of hydrogen on screw dislocations in bcc tungsten, finding that this effect depends on the concentration of hydrogen. Low concentrations of hydrogen enhance dislocation motion, while high concentrations significantly reduce dislocation mobility and lead to a transformation of dislocation structure. Similar structural transitions can be induced by other solutes.