Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
7883364 | Acta Materialia | 2012 | 8 Pages |
Abstract
Precipitates in an Al-Mg-Ge alloy similar to the βⲠphase 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 βâ²-Ge precipitates are coherent with the Al matrix along the needle direction which is parallel to a ã0 0 1ãAl direction, as well as one direction in the cross-section plane that is parallel to a ã1 0 0ãAl direction. This is linked to a smaller lattice parameter in the needle cross-section plane than that of coarser, less coherent βⲠprecipitates 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 βâ²-Ge precipitates are not fully occupied by Ge, the intensity of these columns being consistent with an Al concentration of 30 ± 10%, or a vacancy concentration of 20 ± 10%. The coherent interface is atomically smooth, but with matrix columns containing Ge spaced periodically along the interface.
Keywords
Related Topics
Physical Sciences and Engineering
Materials Science
Ceramics and Composites
Authors
R. Bjørge, C. Dwyer, M. Weyland, P.N.H. Nakashima, C.D. Marioara, S.J. Andersen, J. Etheridge, R. Holmestad,