Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang 110819, China.
State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819, China.
Nano Lett. 2021 Nov 24;21(22):9642-9650. doi: 10.1021/acs.nanolett.1c03448. Epub 2021 Nov 10.
Twinning is a common deformation mechanism in metals, and twin boundary (TB) segregation of impurities/solutes plays an important role in the performances of alloys such as thermostability, mobility, and even strengthening. The occurrence of such segregation phenomena is generally believed as a one-layer coverage of solutes alternately distributed at extension/compression sites, in an orderly, continuous manner. However, in the Mn-free and Mn-containing Mg-Nd model systems, we reported unexpected three- and five-layered discontinuous segregation patterns of the coherent {101̅1} TBs, and not all the extension sites occupied by solutes larger in size than Mg, and even some larger sized solutes taking the compression sites. Nd/Mn solutes selectively segregate at substitutional sites and thus to generate two new types of ordered two-dimensional TB superstructures or complexions. These findings refresh the understanding of solute segregation in the perfect coherent TBs and provide a meaningful theoretical guidance for designing materials via targeted TB segregation.
孪生是金属中常见的变形机制，杂质/溶质在孪晶界（TB）的偏聚对合金的性能（如热稳定性、迁移率，甚至强化）起着重要作用。一般认为，这种偏聚现象的发生是以有序、连续的方式在扩展/压缩位交替分布一层溶质。然而，在无 Mn 和含 Mn 的 Mg-Nd 模型体系中，我们报道了出人意料的、不连续的、具有三层和五层结构的共格 {101̅1}TB 偏聚模式，并非所有的扩展位都被尺寸大于 Mg 的溶质占据，甚至一些较大尺寸的溶质占据了压缩位。Nd/Mn 溶质优先占据替代位，从而产生两种新的有序二维 TB 超结构或配位体。这些发现刷新了对完整共格 TB 中溶质偏聚的理解，并为通过有针对性的 TB 偏聚设计材料提供了有意义的理论指导。
