Abstract

As the building block of a honeycomb precipitate network, the triadic arrangement of β₁ strengthening precipitates is technologically important for the potential development of highly tuneable nanostructure in rare-earth (RE) containing Mg alloys. In this work, we provide systematic experimental observations of those impinged β₁ variants in a Mg-Nd alloy, which are directly related to the characteristic triadic configuration. It is found that the isolated α-Mg crystal in a β₁ triad has a 10.5 deg rotation when it has a perfect equilateral-triangular shape. This rotation angle decreases to ~ 9.4 deg when the isolated α-Mg crystal exhibits a non-equilateral shape. In this case, one or two of its lateral interfaces include a step with a height of 0.56 nm to reduce the lattice mismatch. Furthermore, the pre-stage prior to the formation of β₁ triadic configuration is revealed for the first time. It originates from the implement of two β₁ variants with the same sense of shear. The presence of such two variants, in the absence of the third variant, leads to a rotation of the α-Mg crystal in the small area close to the approaching ends of these two variants. A low-angle symmetrical tilt boundary around the [0001]_α rotation axis is formed between the rotated and unrotated α-Mg crystals. Most of the tilt boundaries observed in this work have a tilt angle of ~ 4.7 deg. The atomic structure of such a tilt boundary is constructed using a crystallographic model and validated by molecular dynamics simulation. The unique distribution of Nd-rich solute clusters along the tilt boundary is qualitatively discussed based on crystallographic analysis.

中文翻译：

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Mg-RE合金中与β1三联体有关的构型

摘要

作为蜂窝网络沉淀的建筑砌块，的三元排列β ₁加强析出物是用于稀土类（RE）含Mg合金高度可调谐纳米结构的潜在发展技术上重要的。在这项工作中，我们提供的那些撞击的系统的实验观察β _1点在镁-Nd合金的变体，这是直接相关的特性三元配置。据发现，分离α -Mg晶体在β ₁三联体具有10.5度旋转时，它具有完美的等边三角形形状。当孤立的α时，该旋转角减小至〜9.4度-镁晶体表现出非等边形状。在这种情况下，其一个或两个横向界面包括一个高度为0.56 nm的台阶，以减少晶格失配。此外，之前的形成前阶段β _1个三元配置显露首次。它源于两种机具β ₁剪切发自内心的变种。在没有第三个变体的情况下，存在这两个变体会导致α- Mg晶体在靠近这两个变体接近端的小区域内旋转。在旋转和未旋转的α之间形成围绕[0001] _α旋转轴的低角度对称倾斜边界-镁晶体。在这项工作中观察到的大多数倾斜边界具有约4.7度的倾斜角。使用晶体学模型构建这种倾斜边界的原子结构，并通过分子动力学模拟对其进行验证。基于晶体学分析定性地讨论了富Nd溶质团簇沿倾斜边界的独特分布。