Zou Lianfeng, Yang Chaoming, Lei Yinkai, Zakharov Dmitri, Wiezorek Jörg M K, Su Dong, Yin Qiyue, Li Jonathan, Liu Zhenyu, Stach Eric A, Yang Judith C, Qi Liang, Wang Guofeng, Zhou Guangwen
Department of Mechanical Engineering & Materials Science and Engineering Program, State University of New York at Binghamton, New York 13902, USA.
Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.
Nat Mater. 2018 Jan;17(1):56-63. doi: 10.1038/nmat5034. Epub 2017 Nov 27.
Surface segregation-the enrichment of one element at the surface, relative to the bulk-is ubiquitous to multi-component materials. Using the example of a Cu-Au solid solution, we demonstrate that compositional variations induced by surface segregation are accompanied by misfit strain and the formation of dislocations in the subsurface region via a surface diffusion and trapping process. The resulting chemically ordered surface regions acts as an effective barrier that inhibits subsequent dislocation annihilation at free surfaces. Using dynamic, atomic-scale resolution electron microscopy observations and theory modelling, we show that the dislocations are highly active, and we delineate the specific atomic-scale mechanisms associated with their nucleation, glide, climb, and annihilation at elevated temperatures. These observations provide mechanistic detail of how dislocations nucleate and migrate at heterointerfaces in dissimilar-material systems.
表面偏析——即相对于体相而言，一种元素在表面的富集——在多组分材料中普遍存在。以铜 - 金固溶体为例，我们证明了由表面偏析引起的成分变化伴随着错配应变，并通过表面扩散和俘获过程在次表面区域形成位错。由此产生的化学有序表面区域起到了有效的屏障作用，抑制了自由表面处随后的位错湮灭。利用动态、原子尺度分辨率的电子显微镜观察和理论建模，我们表明位错具有高度活性，并描绘了在高温下与它们的形核、滑移、攀移和湮灭相关的具体原子尺度机制。这些观察结果提供了位错在异种材料系统的异质界面处如何形核和迁移的机理细节。
