The precipitation of ${\mathrm{\theta }}^{\prime }$${\mathrm{\theta }}^{\prime }$ (Al₂Cu) in Al-Cu alloys is greatly influenced by microalloying elements. Combining high-resolution scanning transmission electron microscopy (STEM) with density functional theory (DFT) and classical nucleation theory (CNT) calculations, we have investigated the generality of a recently discovered mechanism that enhances the precipitation of the ${\mathrm{\theta }}^{\prime }$${\mathrm{\theta }}^{\prime }$ precipitate phase through the dissolution of trace Au additions within ${\mathrm{\theta }}^{\prime }$${\mathrm{\theta }}^{\prime }$. We have designed a workflow to systematically screen chemical elements and found that, Pd and Pt can also enhance the precipitation of ${\mathrm{\theta }}^{\prime }$${\mathrm{\theta }}^{\prime }$ by the same mechanism as Au. All these three elements are found to substitute Cu atoms within ${\mathrm{\theta }}^{\prime }$${\mathrm{\theta }}^{\prime }$, forming what we call “blended precipitates,” namely, precipitates containing regions of both ${\mathrm{\theta }}^{\prime }$${\mathrm{\theta }}^{\prime }$ and another phase of nearly identical crystal structure (i.e., $\mathrm{\eta }$$\mathrm{\eta }$ (Al₂Au), Al₂Pt or Al₂Pd). According to our calculations, enhanced precipitation originates from the lowering of different energy contributions to the substitution of Cu atoms. Among these elements, Pt is the most promising choice for microalloying in the Al-Cu alloy system as it decreases both the formation energy of the ${\mathrm{\theta }}^{\prime }$${\mathrm{\theta }}^{\prime }$ blended precipitate phase as well as the energy of its interface with the Al matrix. This work illustrates the effectiveness of the workflow developed here and should stimulate the exploration of other alloy systems displaying blended precipitate phases, with potentially improved mechanical properties.

中文翻译：

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合理化微合金化添加物在混合沉淀中的作用


Al-Cu 合金中 （Al ₂ Cu） 的 ${\mathrm{\theta }}^{\prime }$ 析出受微合金元素的影响很大。将高分辨率扫描透射电子显微镜 （STEM） 与密度泛函理论 （DFT） 和经典成核理论 （CNT） 计算相结合，我们研究了最近发现的一种机制的普遍性，该机制通过溶解其中的痕量 Au 添加 ${\mathrm{\theta }}^{\prime }$ 物来增强沉淀相的沉淀 ${\mathrm{\theta }}^{\prime }$ .我们设计了一个工作流程来系统地筛选化学元素，发现 Pd 和 Pt 也可以通过与 Au 相同的机制增强沉淀 ${\mathrm{\theta }}^{\prime }$ 。发现所有这三种元素都可以在 ${\mathrm{\theta }}^{\prime }$ 内取代 Cu 原子，形成我们所说的“混合沉淀物”，即含有两者 ${\mathrm{\theta }}^{\prime }$ 和另一个晶体结构几乎相同的相（即 $\mathrm{\eta }$ （Al ₂ Au）、Al ₂ Pt 或 Al ₂ Pd）区域的沉淀物。根据我们的计算，增强的沉淀源于对 Cu 原子取代的不同能量贡献的降低。在这些元素中，Pt 是 Al-Cu 合金系统中最有前途的微合金化选择，因为它会降低 ${\mathrm{\theta }}^{\prime }$ 混合沉淀相的形成能量及其与 Al 基体界面的能量。这项工作说明了此处开发的工作流程的有效性，并应刺激对其他显示混合沉淀相的合金系统的探索，并可能改善机械性能。