HAADF-STEM study of β′-type precipitates in an over-aged Al-Mg-Si-Ag alloy

被引：44
作者：
Marioara, C. D. [1 ]
Nakamura, J. [2 ]
Matsuda, K. [3 ]
Andersen, S. J. [1 ]
Holmestad, R. [4 ]
Sato, T. [5 ]
Kawabata, T. [3 ]
Ikeno, S. [3 ]
机构：
[1] SINTEF Mat & Chem, N-7465 Trondheim, Norway
[2] Toyama Univ, Grad Sch Sci & Engn Educ, Toyama 9308555, Japan
[3] Toyama Univ, Grad Sch Sci & Engn Res, Toyama 9308555, Japan
[4] Norwegian Univ Sci & Technol, Fac Phys, N-7491 Trondheim, Norway
[5] Tokyo Inst Technol, Grad Sch Sci & Engn, Meguro Ku, Tokyo 1528550, Japan
来源：
PHILOSOPHICAL MAGAZINE | 2012年 / 92卷 / 09期
关键词：
high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM); high resolution; precipitate; aluminium-magnesium-silicon alloy; silver addition; CRYSTAL-STRUCTURE; PHASE;
D O I：
10.1080/14786435.2011.642319
中图分类号：
T [工业技术];
学科分类号：
08 ;
摘要：
Coarse, rod-shaped precipitates growing along < 100 > Al directions in an Al-1.0wt% Mg2Si alloy with 0.5wt% Ag additions were investigated by high-resolution high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). All investigated precipitates had complex structures, being composed of domains separated by anti-phase resembling boundaries. The domains consist of a modified hexagonal beta'-type structure that contains a considerable amount of Ag. Based on HAADF-STEM images, an average atomic model with space group P-62 m (189) and composition Al3Mg3Si2Ag is proposed, having Al incorporation and Ag replacing certain Si atomic columns. Co-existence with the Ag-free beta'-Mg9Si5 phase has been observed for some precipitates. The boundaries may be described as full or half units of the orthorhombic U2-AlMgSi precipitate phase. The HAADF-STEM images indicate partial replacements of Al atoms by Ag, in both the beta'-type domains and the U2-type boundaries. Ag enrichment of the Al matrix near the precipitate/Al interface was observed for all the investigated precipitates
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收藏
页码：1149 / 1158
页数：10
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