Ω, T1, Y, η' and η nano-phases in different series Al alloys are known to all precipitate along the major slip planes {111}Al. Their precipitation in multi-element cross-over Al alloys could thus be very intricate. In this work, atomic resolution HAADF-STEM and first-principles calculations were combined to comprehensively investigate their atomic structures and energetics in a set of model Al alloys. Our results revealed that they all tend to initially form a 2D layered structure consisting of an isostructural (Al,Cu) O-unit along the {111}, and that their further evolution sensitively depends on alloy composition. Alloying with Mg and/or Ag stabilizes the O-units to form a single-layer Ω (SL-Ω or Ω') in Al-Cu-Mg(-Ag) alloys. Alloying with Li stabilizes O-units to form SL-T1 in Al-Cu-Li alloys. Alloying with Mg and Zn stabilizes O-units to form SL-Y in Al-Zn-Mg-Cu alloys. For cross-over Al alloys with a low Mg+Zn and low Li content, O-units would grow into O-O pairs to induce the SL-Ω (Ω') → multi-layer (ML)-Ω transformation. Increasing the Li content helps SL-T1 grow continuously or transform into ML-T1 with an O-O'-O stacking. Both mechanisms take actions to suppress ML-Ω. For cross-over Al alloys with high Mg+Zn content, O-units grow into O-R pairs and further into R-R−1 pairs, inducing the transformation of SL-Ω/T1/Y → η' → η in strong preference over Ω and T1 in Al-Zn-Mg-Cu(-Ag)(-Li) alloys. These results can fundamentally explain diverse experimental observations and provide many profound perspectives on the competitive precipitation in cross-over Al alloys.

中文翻译：

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沿共同习{111}性面的纳米相之间的结构相关性及其对交叉 Al 合金设计的影响


已知不同系列铝合金中的 Ω、T1、Y、η' 和 η 纳米相都沿主要滑移面 {111}Al 析出。因此，它们在多元素交叉 Al 合金中的析出可能非常复杂。在这项工作中，原子分辨率 HAADF-STEM 和第一性原理计算相结合，全面研究了它们在一组模型 Al 合金中的原子结构和能量学。我们的结果表明，它们最初都倾向于形成由沿{111}的等构 （Al，Cu） O 单元组成的 2D 层状结构，并且它们的进一步演变敏感地取决于合金成分。与 Mg 和/或 Ag 的合金化使 O 单元稳定，在 Al-Cu-Mg（-Ag） 合金中形成单层Ω（SL-Ω 或 Ω'）。与 Li 合金化可稳定 O 单元，在 Al-Cu-Li 合金中形成 SL-T1。与 Mg 和 Zn 的合金化使 O 单元稳定，在 Al-Zn-Mg-Cu 合金中形成 SL-Y。对于低 Mg+Zn 和低 Li 含量的交叉 Al 合金，O 单元将生长成 O-O 对，以诱导 SL-Ω （Ω'） →多层 （ML）-Ω 转变。增加 Li 含量有助于 SL-T1 持续生长或通过 O-O'-O 堆叠转化为 ML-T1。这两种机制都会采取措施来抑制 ML Ω。对于具有高 Mg+Zn 含量的交叉 Al 合金，O 单元生长为 O-R 对，并进一步形成 R-R-1 对，诱导 SL-Ω/T1/Y → η' → η 在 Al-Zn-Mg-Cu（-Ag）（-Li） 合金中优先于 Ω 和 T1 发生转变。这些结果可以从根本上解释不同的实验观察结果，并为交叉 Al 合金中的竞争沉淀提供许多深刻的视角。