Aberration-corrected scanning transmission electron microscopy study of 尾鈥?like precipitates in an Al-Mg-Ge alloy

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• 作者：R. Bjø ; rge^a ; C. Dwyer^b ; ^c ; ^d ; M. Weyland^b ; ^c ; P.N.H. Nakashima^c ; ^d ; C.D. Marioara^e ; S.J. Andersen^e ; J. Etheridge^b ; ^c ; R. Holmestad^a ; ^{randi.holmestad@ntnu.no}
• 关键词：Aluminium alloys ; Precipitation ; High angle annular dark field ; Scanning transmission electron microscopy
• 刊名：Acta Materialia
• 出版年：2012
• 期刊代码：1_13596454
• 类别：ms
• 出版时间：April, 2012
• 卷：60
• 期：6-7
• 页码：3239-3246
• 文件大小：1569 K

摘要

Precipitates in an Al-Mg-Ge alloy similar to the 尾鈥?phase in Al-Mg-Si alloys were investigated using qualitative and quantitative aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF STEM). The needle-shaped 尾鈥?Ge precipitates are coherent with the Al matrix along the needle direction which is parallel to a 銆? 0 1銆?sub>Al direction, as well as one direction in the cross-section plane that is parallel to a 銆? 0 0銆?sub>Al direction. This is linked to a smaller lattice parameter in the needle cross-section plane than that of coarser, less coherent 尾鈥?precipitates in Al-Mg-Si alloys, despite Ge having a larger atomic radius than Si. Quantitative HAADF STEM results show that the nominal Ge columns of the 尾鈥?Ge precipitates are not fully occupied by Ge, the intensity of these columns being consistent with an Al concentration of 30 卤 10%, or a vacancy concentration of 20 卤 10%. The coherent interface is atomically smooth, but with matrix columns containing Ge spaced periodically along the interface.