He Cong, Li Zhiqiao, Chen Houwen, Wilson Nick, Nie Jian-Feng
International Joint Laboratory for Light Alloys (Ministry of Education), College of Materials Science and Engineering, Chongqing University, Chongqing, P.R. China.
Electron Microscopy Center, Chongqing University, Chongqing, P.R. China.
Nat Commun. 2021 Feb 1;12(1):722. doi: 10.1038/s41467-021-21104-8.
Interface segregation of solute atoms has a profound effect on properties of engineering alloys. The occurrence of solute segregation in coherent twin boundaries (CTBs) in Mg alloys is commonly considered to be induced by atomic size effect where solute atoms larger than Mg take extension sites and those smaller ones take compression sites in CTBs. Here we report an unusual solute segregation phenomenon in a group of Mg alloys-solute atoms larger than Mg unexpectedly segregate to compression sites of {10[Formula: see text]1} fully coherent twin boundary and do not segregate to the extension or compression site of {10[Formula: see text]2} fully coherent twin boundary. We propose that such segregation is dominated by chemical bonding (coordination and solute electronic configuration) rather than elastic strain minimization. We further demonstrate that the chemical bonding factor can also predict the solute segregation phenomena reported previously. Our findings advance the atomic-level understanding of the role of electronic structure in solute segregation in fully coherent twin boundaries, and more broadly grain boundaries, in Mg alloys. They are likely to provide insights into interface boundaries in other metals and alloys of different structures.
溶质原子的界面偏析对工程合金的性能有深远影响。镁合金中溶质在共格孪晶界（CTB）处发生偏析，通常被认为是由原子尺寸效应引起的，即比镁大的溶质原子在CTB中占据伸长位置，而较小的溶质原子占据压缩位置。在此，我们报道了一组镁合金中一种不寻常的溶质偏析现象——比镁大的溶质原子意外地偏析到{10[公式：见正文]1}完全共格孪晶界的压缩位置，而不偏析到{10[公式：见正文]2}完全共格孪晶界的伸长或压缩位置。我们提出，这种偏析主要由化学键（配位和溶质电子构型）主导，而非弹性应变最小化。我们进一步证明，化学键因素也能预测先前报道的溶质偏析现象。我们的发现推进了对电子结构在镁合金完全共格孪晶界以及更广泛的晶界中溶质偏析作用的原子级理解。它们可能为其他不同结构的金属和合金中的界面边界提供见解。
