In-situ high-resolution transmission electron microscopy investigation of grain boundary dislocation activities in a nanocrystalline CrMnFeCoNi high-entropy alloy

Relaxation activities of grain boundary dislocations in a nanocrystalline CrMnFeCoNi high-entropy alloy were investigated using in-situ high-resolution transmission electron microscopy. 1/3 < 111 > Frank dislocations at a low-angle grain boundary were relaxed by, climbing or emitting Shockley partials that produced stacking faults slightly narrower than the theoretically predicted width. The extended dislocation structures were quite stable since no any change of the Shockley partial position or the stacking fault width was induced under further e-beam irradiation. These behaviours indicate easy activation of Shockley partials and strong barriers for dislocation motion in the alloy, which explains well the excellent deformability and strengthening effect of the alloy. In contrast, Frank dislocations at a twin boundary maintained a compact core structure, but were accompanied with a rotation process of the adjacent grain. (C) 2017 Elsevier B.V. All rights reserved.