Correlated necklace dislocations in highly oriented nanotwinned metals

择优取向纳米孪晶金属中的“链式”关联位错

In this paper, we review recent progress in the understanding of a novel dislocation mechanism, named correlated necklace dislocations(CNDs), activated in highly oriented nanotwinned(NT) metals under monotonic and cyclic loading applied parallel to the twin boundaries(TBs). This mechanism was initially revealed to be responsible for the continuous strengthening behavior of NT metals when the TB spacing(λ) is reduced to around 1 nm. It was later found that the presence of a crack-like defect could trigger the operation of CNDs at much larger TB spacings. Most recently, atomistic modeling and experiments demonstrated a history-independent and stable cyclic response of highly oriented NT metals governed by CNDs formed in the NT structure under cyclic loading. CNDs move along the twin planes without directional lattice slip resistance, thus contributing to a symmetric cyclic response of the NT structure regardless of pre-strains imposed on the sample before cyclic loading. We conclude with potential research directions in the investigation of this unique deformation mechanism in highly oriented NT metals.

本文综述了择优取向纳米孪晶金属中"链式"关联位错(CNDs)的研究进展。当拉伸方向与孪晶界方向水平,且孪晶厚度(λ)为1 nm左右时,关联位错会大量开动,引起材料持续强化。在较宽的孪晶片层中,裂纹等初始缺陷可引起应力集中,诱发关联位错形核。此外,循环变形也会促进关联位错在纳米孪晶结构中的形成,使后者具有与历史无关、稳定和拉压对称的循环响应。最后,本文提出了择优取向纳米孪晶金属中与"链式"关联位错相关的潜在研究方向。