Solute clusters and GP zones in binary Mg-RE alloys
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- 作者：J.F. Niea ; jianfeng.nie@monash.edu" class="auth_mail" title="E-mail the corresponding author ; N.C. Wilsonb ; Y.M. Zhua ; Z. Xua
- 关键词：Magnesium alloys ; Solute clusters ; GP zones ; Precipitation
- 刊名：Acta Materialia
- 出版年：2016
- 出版时间：March 2016
- 年：2016
- 卷：106
- 期：Complete
- 页码：260-271
- 全文大小：5121 K
文摘
Solute clusters and Guinier–Preston (GP) zones play an important role in determining mechanical properties of Mg–RE (where RE represents rare earth elements) alloys. In this study, we use aberration-corrected scanning transmission electron microscopy to characterize solute clusters and GP zones in binary Mg-0.52 at.%Nd and Mg-2.32 at.%Y alloys, and rationalize the experimental observations using first-principles density functional theory computations. It is found that the solute clusters formed in the early stage of precipitation, in each of the two alloys, have a family of short-range order structures comprising [0001]α atomic columns rich in Nd or Y atoms. The separation distance of two adjacent Nd- or Y-rich columns in each structure is invariably 3.70 Å along the <
>α direction. The GP zones formed in the binary Mg–Nd alloy have an irregular zig-zag mono-layer shape and a range of structures, each of which comprises solute clusters of the same or mixed types, with a unique separation distance of 6.68 Å between two adjacent clusters. GP zones also form in the binary Mg–Y alloy, but they all have a single and yet ordered structure comprising an array of regularly spaced zig-zag columns in a mono-layer rich in Y atoms, which resembles that of a single layer in the β′ phase in this alloy. The density functional theory computation results indicate that the observed arrangements of RE-rich columns within the solute clusters and GP zones are controlled by minimization of elastic strain associated with individual solute atoms.
>α direction. The GP zones formed in the binary Mg–Nd alloy have an irregular zig-zag mono-layer shape and a range of structures, each of which comprises solute clusters of the same or mixed types, with a unique separation distance of 6.68 Å between two adjacent clusters. GP zones also form in the binary Mg–Y alloy, but they all have a single and yet ordered structure comprising an array of regularly spaced zig-zag columns in a mono-layer rich in Y atoms, which resembles that of a single layer in the β′ phase in this alloy. The density functional theory computation results indicate that the observed arrangements of RE-rich columns within the solute clusters and GP zones are controlled by minimization of elastic strain associated with individual solute atoms.