Abstract Microalloying is a routine method to optimize precipitation and mechanical properties in light metals. Here we study how In and Sb (0.025 at.%) additions in an Al-1.7 at.% Cu alloy benefit precipitation during ageing and investigate the underlying mechanism using scanning transmission electron microscopy and density functional theory (DFT) calculations. The combined additions accelerate precipitation kinetics and increase peak hardness through two different ways. In samples aged directly at low temperatures (≤200 °C) after solid solution treatment, cubic close-packed InSb nanocrystals form first. The truncated {002} surfaces of InSb particles induce the preferential nucleation of Guinier-Preston (GP) zones, θ″ and θ′ successively. However, in samples aged at 250 °C, precipitation of θ′ precedes that of InSb particles. Supersaturated vacancies trapped by In and Sb solute atoms/clusters play a critical role in switching the precipitation sequence. By tuning how strong the binding between a vacancy and solute atoms is, we successfully invert the temperature dependence of the precipitation sequence. These findings will contribute to understanding precipitation mechanisms and optimizing precipitate distribution in aluminium precipitation hardenable alloys.

中文翻译：

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Al-1.7 Cu-0.025In-0.025Sb (at.%) 合金中空位调谐的析出途径

摘要 微合金化是优化轻金属析出和力学性能的常规方法。在这里，我们研究了在 Al-1.7 at.% Cu 合金中添加 In 和 Sb (0.025 at.%) 如何在时效过程中促进沉淀，并使用扫描透射电子显微镜和密度泛函理论 (DFT) 计算研究潜在机制。联合添加通过两种不同的方式加速沉淀动力学并增加峰值硬度。在固溶处理后直接在低温（≤200°C）下老化的样品中，首先形成立方密堆积的 InSb 纳米晶体。InSb 颗粒的截断 {002} 表面依次诱导 Guinier-Preston (GP) 区域 θ″ 和 θ' 的优先成核。然而，在 250 °C 时效的样品中，θ' 的沉淀先于 InSb 颗粒的沉淀。被 In 和 Sb 溶质原子/簇捕获的过饱和空位在转换沉淀序列中起着关键作用。通过调整空位和溶质原子之间的结合强度，我们成功地反转了沉淀序列的温度依赖性。这些发现将有助于理解沉淀机制和优化铝沉淀硬化合金中的沉淀分布。