This work reports a novel effect of impurity element Cd on enhancing the precipitation kinetics and increasing the peak hardness of Al–Mg–Si(–Cu) alloys during artificial ageing. It is found that the number density of age hardening Mg–Si(–Cu) precipitates is greatly increased by Cd addition (~0.06 at.%) at both the under-aged and peak-aged stages. A systematic study on the precipitation behaviour by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) shows that most Mg–Si(–Cu) precipitates in the Cd-containing Al–Mg–Si alloys are associated with Cd-rich precipitates and have highly disordered structures. It is also found that the formation of Q'/C-like sub-units in Mg–Si(–Cu) precipitates is significantly promoted by Cd additions. To explore the nucleation mechanism under the influence of Cd addition, atom probe tomography (APT) is applied to study the solute clustering behaviour in the early stages of artificial ageing, and density functional theory (DFT) calculations are used to evaluate the binding energies of different solute-vacancy complexes and therefore the formation kinetics of Mg–Si–Cd clusters.

这项工作报告了杂质元素Cd在人工时效过程中对提高析出动力学和增加Al-Mg-Si（-Cu）合金的峰值硬度的新作用。研究发现，在年龄不足和峰值年龄阶段，通过添加Cd（〜0.06 at。％），使时效硬化的Mg-Si（-Cu）析出物的数量密度大大增加。通过高角度环形暗场扫描透射电子显微镜（HAADF-STEM）对沉淀行为的系统研究表明，含Cd的Al-Mg-Si合金中大多数Mg-Si（-Cu）沉淀与Cd有关富含沉淀物，并具有高度无序的结构。还发现，添加Cd可以显着促进Mg-Si（-Cu）沉淀物中Q'/ C样亚基的形成。为了探索在添加镉的影响下的成核机理，