Density functional theory study of solute cluster growth processes in Mg-Y-Zn LPSO alloys
Density functional theory study of solute cluster growth processes in Mg-Y-Zn LPSO alloys
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DOI：
10.1016/j.actamat.2020.116491
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发表时间：
2021-01-15
期刊：
影响因子：
9.4
通讯作者：
Abe, Eiji
中科院分区：
文献类型：
--
作者：
Itakura, Mitsuhiro;Yamaguchi, Masatake;Abe, Eiji
长周期堆积有序（LPSO）合金中的溶质原子团簇在其特殊的塑性行为中起着关键作用，例如扭结的形成和扭结的强化。识别簇结构的原子细节是LPSO合金原子建模的先决条件，对于提高其强度和延展性至关重要;然而，簇中的间隙原子存在很大的不确定性。虽然密度泛函理论计算已经表明，Mg间隙原子的夹杂物在大多数LPSO合金中在能量上是最有利的，但也已经在间隙位点实验观察到溶质元素。为了预测团簇中间隙原子的分布，并确定存在的元素的种类，有必要确定间隙原子产生的机制。在目前的工作中，我们使用密度泛函理论计算研究溶质团簇的生长过程，特别是Mg-Y-Zn LPSO合金，以确定其溶质团簇的精确原子结构。我们表明，一对间隙原子和空位自发地创建时，一定数量的溶质原子被吸收到集群，所有的完整的集群应包括间隙原子。我们还表明，间隙原子主要是镁，而其余的是Y;间隙Zn原子可以忽略不计。这一知识大大简化了Mg-Y-Zn合金中溶质团簇的原子模型。由于空位从团簇中释放出来，空位密度在溶质团簇生长的区域应该是过饱和的，并且空位密度的增加加速了团簇的生长。(C)2020 Acta Materialia Inc.爱思唯尔有限公司出版
Solute clusters in long period stacking order (LPSO) alloys play a key role in their idiosyncratic plastic behavior, for example kink formation and kink strengthening. Identifying atomistic details of cluster structures is a prerequisite for atomistic modeling of LPSO alloys and is crucial for improving their strength and ductility; however, there is much uncertainty regarding interstitial atoms in the cluster. Although density functional theory calculations have shown that the inclusion of Mg interstitial atoms is energetically most favorable in majority of LPSO alloys, solute elements have also been experimentally observed at interstitial sites. To predict the distributions of interstitial atoms in the cluster and to determine the kind of elements present, it is necessary to identify mechanisms by which interstitial atoms are created. In the present work, we use density functional theory calculations to investigate growth processes of solute clusters, specifically the Mg-Y-Zn LPSO alloy, in order to determine the precise atomistic structure of its solute clusters. We show that a pair of an interstitial atom and a vacancy are spontaneously created when a certain number of solute atoms are absorbed into the cluster, and that all full-grown clusters should include interstitial atoms. We also demonstrate that interstitial atoms are mostly Mg, while the rest are Y; interstitial Zn atoms are negligible. This knowledge greatly simplifies the atomistic modeling of solute clusters in Mg-Y-Zn alloys. Owing to the vacancies emitted from the cluster, vacancy density should be super-saturated in regions where solute clusters are growing, and increased vacancy density accelerates cluster growth. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd.