Exploring the redistribution mechanism of Mg from the perspective of experimental observation has been a long-term yet challenging attempt in Al-Mg alloys. Here we demonstrate a simple but effective approach to obtain non-uniform Mg solute distribution (i.e., Mg-enriched/depletion zones) around typical grain boundaries (GBs) in a nanocrystalline Al-8 Mg alloy. This abnormal segregation was detected by both high-angle annular dark-field scanning transmission electron microscopy and atom probe tomography. The results show that local strain and GB migration during deformation leads to spatially inhomogeneous Mg solute distribution around the GBs. Both the non-uniform distribution and the broadened GBs can hinder GB migration and dislocation motion, thus enhance the strength. An inhomogeneous solute distribution mechanism of Mg atoms is proposed based on the extensive investigations. This study may help with developing new strengthening mechanisms of nanocrystalline materials.

从实验观察的角度探索Mg的再分布机制一直是Al-Mg合金中一项长期但具有挑战性的尝试。在这里，我们展示了一种简单但有效的方法来获得纳米晶 Al-8 Mg 合金中典型晶界 (GB) 周围的非均匀 Mg 溶质分布（即，Mg 富集/贫化区）。通过高角度环形暗场扫描透射电子显微镜和原子探针断层扫描检测到这种异常偏析。结果表明，变形过程中的局部应变和 GB 迁移导致 GB 周围空间不均匀的 Mg 溶质分布。晶界的不均匀分布和加宽都可以阻碍晶界的迁移和位错运动，从而提高强度。基于广泛的研究，提出了 Mg 原子的不均匀溶质分布机制。这项研究可能有助于开发纳米​​晶材料的新强化机制。