Understanding the Role of Short-Range Order in the Nucleation and Transformation of the B '/Q ' Precipitates in Al-Mg-Si(-Cu) Alloys
Understanding the Role of Short-Range Order in the Nucleation and Transformation of the B '/Q ' Precipitates in Al-Mg-Si(-Cu) Alloys
复制标题
了解短程有序在 Al-Mg-Si(-Cu) 合金中 B '/Q ' 析出物的形核和转变中的作用
DOI：
10.1007/s11661-021-06309-2
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发表时间：
2021
影响因子：
2.8
通讯作者：
Liu Qing
中科院分区：
文献类型：
--
作者：
Ding Lipeng;Weng Yaoyao;Jia Zhihong;Zang Ruojin;Liu Qing
由于Al-Mg-Si（-Cu）合金中析出相的无序性和析出过程的复杂性，对Al-Mg-Si（-Cu）合金中亚稳硬化析出相演变的认识仍然十分混乱和难以捉摸。利用原子分辨扫描透射电子显微镜研究了Al-Mg-Si（-Cu）合金中B′/Q′相的形核和转变机制。指出理解沉淀相中短程有序的形成和演化是揭示其相变机制的核心。虽然B′和Q′相具有相同的晶体结构，且均来源于β“相，但这两种相的形成机制不同。对于Al-Mg-Si合金中形成的B′，β″相首先通过“低密度圆柱体”（LDC）向Mg六边形的转变而转变为U2相。随后，通过Al-Si柱的旋转，以及三角形B′亚基的形成和有序化，U2相转变为B′相。对于Al-Mg-Si-Cu合金中形成的Q′，Cu原子首先进入β″相内部，形成Cu亚基团簇的亚结构。在大多数情况下，这些Cu亚基团簇是随机分布的，并且在整个沉淀物中形成QM和QP晶格。然而，在一些沉淀物中，Cu亚单元簇的排列构成六方晶格并导致QC相的形成。在随后的时效过程中，三角形Q′亚基的形成和有序化可导致Q′相的形成。阐明SRO在这些过程中的作用，为理解Al-Mg-Si（-Cu）合金中析出相的转变机制提供了新的见解。
The understanding of metastable hardening precipitate evolution in Al-Mg-Si(-Cu) is still quite confused and elusive due to the disordered nature of several precipitates and the complex processes involved. Atomic-resolution scanning transmission electron microscopy is used here to study the nucleation and transformation mechanisms of the B′/Q′ precipitates in the Al-Mg-Si(-Cu) alloys. It is emphasized that understanding the formation and evolution of short-range order (SRO) in the precipitates is a core to revealing their transformation mechanisms. Although the B′ and Q′ phases have the same crystal structure, and both originate from the β″ precipitate, the formation mechanisms of these two precipitates are different. For B′, formed in the Al-Mg-Si alloy, the β″ phase initially transforms to the U2 phase by the transition of the “low density cylinder” (LDC) to Mg hexagons. Subsequently, the U2 phase transforms to the B′ phase by the rotation of Al-Si columns, and the formation and ordering of triangle B′ sub-units. For Q′, formed in the Al-Mg-Si-Cu alloy, the Cu atoms incorporate initially the interior of the β″ phase and form the substructure of Cu sub-unit clusters. In most cases, these Cu sub-unit clusters are randomly distributed, and the QM and QP lattices are formed throughout the precipitates. In some precipitates, the arrangement of Cu sub-unit clusters however constitutes a hexagonal lattice and leads to the formation of the QC phase. During subsequent aging, the formation and ordering of the triangle Q′ sub-units can lead to the formation of the Q′ phase. Clarifying the role of the SRO in these processes provides a new insight in the understanding of transformation mechanisms of precipitates in Al-Mg-Si(-Cu) alloys.