微合金化是提高铝合金强度的一种有效方法。 然而，ZL205A 合金中最重要的微量元素 Cd 对析出强化的影响尚不完全清楚。 本研究系统探讨了 Cd 元素对 ZL205A 合金微观组织与拉伸性能的影响。 结果表明，Cd 微合金化使合金屈服强度显著提升约 130 MPa。 微观组织分析发现，T6 态 ZL205A 合金的主要析出相为 θ″相，而 Cd 元素的添加促

进了 θ″→ θ′相转变，使 θ′相成为主要析出相。 这使得合金析出强化机制从位错切过 θ″相转变为位错绕过 θ′相，从而有效提升强化效果。 基于 STEM-EDS 表征，提出 Cd 通过 2 个协同机制促进相变，即①Cd 因其较高的空位结合能，形成具有高扩散速率的 Cd-Cu- 空位簇，为转变提供 Cu 原子；②Cd- 空位对在 θ′相形成温度下解离并释放空位，提高 Cu 原子在 Al 基体中的扩散速率，从而促进 θ″相向 θ′相的转变。

Microalloying is an effective and feasible strengthening strategy for Al alloys. However, the influence of Cd, which is the most important trace element of ZL205A, on precipitation hardening is not fully understood. On this basis, the effects of Cd on the microstructure and tensile properties of the ZL205A alloy were systematically investigated. The results show that the microalloying of Cd significantly enhances the strength by ~130 MPa. Microstructure analysis indicates that the main precipitate of the T6 ZL205A alloy is the θ″ phase, and the addition of Cd element promotes the θ″→ θ′ phase transformation, resulting in θ′ becoming the dominant precipitate. This makes the alloy precipitation strengthening mechanism change from dislocation shearing through the θ″ phase to dislocation bypassing the θ′ phase, thereby effectively enhancing the strengthening effect. On the basis of the STEM-EDS characterization, it is suggested that Cd promotes the θ″ → θ′ phase transformation through two synergistic mechanisms: ① Cd has high vacancy binding energies, leading to the formation of Cd-Cu-vacancy clusters, providing Cu atoms for transformation; ② the Cd-vacancy pairs dissociate at the temperature of the θ′ phase formation and release vacancies, which increases the diffusion rate of the Cu atoms in the Al matrix, thus promoting the transformation of θ″ to θ′.