Adding alloying elements to improve the performances or the manufacturing processes of Al-Mg-Si alloys has long been a serious issue in developing advanced automotive aluminum materials. The Zn element, among those promising ones, has demonstrated positive alloying effects on Al-Mg-Si alloys. However, the atomic-scale roles of Zn in an age-hardened Al-Mg-Si-Zn alloy have not been adequately understood. Using atomic-resolution electron microscopy, here we report the precise locations of Zn elements in all hardening precipitates involved and their alloying mechanism at the atomic scale when alloying the alloy. Our results show that Zn atoms enter all the major hardening phases to occupy specific featured atomic sites of the original elements, e.g. the Si1 and Mg2 sites in the β'-2 phase, and modify their crystal structures, interfacial structures and morphologies in characteristic manners. It is revealed that for the β'-phase, Zn atoms occupy unique atomic sites, whereas for other phases, they demonstrate similar behaviors as other additive alloying elements such as Ag and Cu do.

在开发先进的汽车铝材料中，添加合金元素以改善Al-Mg-Si合金的性能或制造工艺一直是一个严重的问题。在那些有前途的锌元素中，锌元素已证明对Al-Mg-Si合金具有积极的合金作用。但是，对在时效硬化的Al-Mg-Si-Zn合金中Zn的原子尺度作用还没有充分了解。使用原子分辨率电子显微镜，我们在此报告了在合金化合金时，所涉及的所有硬化沉淀物中Zn元素的精确位置及其在原子尺度上的合金化机理。我们的结果表明，Zn原子进入所有主要的硬化相，从而占据了原始元素的特定特征原子位，例如β'-2相中的Si1和Mg2位，并改变了它们的晶体结构，界面结构和形态以独特的方式表现出来。结果表明，对于β'相，Zn原子占据独特的原子位置，而对于其他相，它们表现出与其他添加剂合金元素（如Ag和Cu）相似的行为。