Mg alloys are promising lightweight structural materials due to their low density and excellent mechanical properties. However, their limited formability and ductility necessitate improvements in these properties, specifically through texture modification via grain boundary segregation. While significant efforts have been made, the segregation behavior in Mg polycrystals, particularly with basal texture, remains largely unexplored. In this study, we performed atomistic simulations to investigate grain boundary segregation in dilute and concentrated solid solution Mg–Al alloys. We computed the segregation energy spectrum of basal-textured Mg polycrystals, highlighting the contribution from specific grain boundary sites, such as junctions, and identified a newly discovered bimodal distribution which is distinct compared to the conventional skew-normal distribution found in randomly-oriented polycrystals. Using a hybrid molecular dynamics/Monte Carlo approach, we simulated segregation behavior at finite temperatures, identifying grain boundary structural transitions, particularly the varied fraction and morphology of topologically close-packed grain boundary phases when changing thermodynamic variables. The outcomes of this study offer crucial insights into basal-textured grain boundary segregation and phase formation, which can be extended to other relevant Mg alloys containing topologically close-packed intermetallics.

中文翻译：

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基底组织镁合金的晶界偏析谱：从溶质装饰到结构转变


镁合金由于其低密度和优异的机械性能，是很有前途的轻质结构材料。然而，它们有限的成型性和延展性需要改进这些性能，特别是通过晶界偏析进行织构改性。尽管已经做出了重大努力，但 Mg 多晶中的偏析行为，尤其是具有基底结构的偏析行为，在很大程度上仍未得到探索。在这项研究中，我们进行了原子模拟，以研究稀固溶体 Mg-Al 合金中的晶界偏析。我们计算了基底纹理 Mg 多晶的偏离能谱，突出了特定晶界位点（如结）的贡献，并确定了一种新发现的双峰分布，该分布与随机取向多晶中发现的常规偏正态分布相比是不同的。使用混合分子动力学/蒙特卡洛方法，我们模拟了有限温度下的偏析行为，确定了晶界结构转变，特别是当改变热力学变量时拓扑紧密堆积的晶界相的分数和形态的变化。这项研究的结果为基底织构晶界偏析和相形成提供了重要的见解，这可以扩展到其他含有拓扑紧密堆积金属间化合物的相关 Mg 合金。