Nonsymmetrical Segregation of Solutes in Periodic Misfit Dislocations Separated Tilt Grain Boundaries
Hongbo Xie, Qiuyan Huang, Junyuan Bai, Shanshan Li, Yang Liu, Jianguang Feng, Yuansheng Yang, Hucheng Pan, Hongxiao Li, Yuping Ren, Gaowu Qin
Abstract
Interfacial segregation is ubiquitous in mulit-component polycrystalline materials and plays a decisive role in material properties. So far, the discovered solute segregation patterns at special high-symmetry interfaces are usually located at the boundary lines or are distributed symmetrically at the boundaries. Here, in a model Mg-Nd-Mn alloy, we confirm that elastic strain minimization facilitated nonsymmetrical segregation of solutes in four types of linear tilt grain boundaries (TGBs) to generate ordered interfacial superstructures. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy observations indicate that the solutes selectively segregate at substitutional sites at the linear TGBs separated by periodic misfit dislocations to form such two-dimensional planar structures. These findings are totally different from the classical McLean-type segregation which has assumed the monolayer or submonolayer coverage of a grain boundary and refresh understanding on strain-driven interface segregation behaviors.