Light, environmentally friendly and recyclable materials are of increasing importance, such as in the automotive industry where the age-hardenable Al-Mg-Si alloys are of high interest. By understanding better how microstructure responds to changed processing or composition, costs can be cut and macroscopic properties tailored for particular applications. For example, by reducing the solute amount a softer material will allow higher extrusion speeds, however, on the expense of material strength. Recently, it was shown how adding back a lower at% of ‘exotic’ elements like Li, Cu, Ag and Ge compensates such strength loss . Age hardening is ascribed to dislocation resisting strain-fields set up in the aluminium during nucleation and growth of the metastable, nanoscale, semi-coherent precipitate needles in the three <100> Al directions . The replacement elements change precipitate structure and growth conditions.
Precipitate statistics based on transmission electron microscopy (TEM) can elucidate how material strength is related to precipitate number densities, sizes and volume fractions; see example a bright field TEM micrograph in Fig. 1 (a) used for this purpose. The elemental contrast in probe Cs corrected high angle annular dark field scanning TEM (HAADF-STEM) greatly assists structural characterization of individual precipitate cross sections , enabling identification of precipitate type and the composition of individual atomic columns. See example of a β’’ precipitate in Fig. 1 (b).
Because elements with similar atomic number (Z) express very small intensity differences, electron energy loss spectroscopy (EELS) elemental mapping has been applied to aid resolution. It became clear that EELS in combination with HAADF-STEM can resolve the hexagonal network of Si columns  well, see Fig. 2. It was also found that a significant proportion of the other atomic columns were mixed.
A pressing matter in material design is enhanced control with precipitate characteristics which vary strongly with alloy composition and processing. Density functional theory (DFT) simulations have a great potential for broadening the understanding concerning precipitate nucleation, growth and final microstructure, and how they are connected. Here we have investigated binding between solute atoms and to vacancies, along with volume misfits (see Fig. 4) in the Al lattice, in a venture to relate these parameters to precipitation.
 E. A. Mørtsell, C. D. Marioara, S. J. Andersen, J. Røyset, O. Reiso and R. Holmestad, Metallurgical and Materials Transactions A, vol. 46, no. 9, pp. 4369 – 4379, 2015.
 C. D. Marioara, H. Nordmark, S. J. Andersen and R. Holmestad, J. Mater. Sci., vol. 41, pp. 471 – 478, 2006.
 P. D. Nellist and S. J. Pennycook, “The principles and interpretation of annular dark-field Z-contrast imaging,” Advances in Imaging and Electron Physics, vol. 113, pp. 147 – 203, 2000.
 S. J. Andersen, C. D. Marioara, R. Vissers, A. L. Frøseth and P. Derlet, in Proc. 13th Eur. Mocr. Congress (EMC) 2, 2004.
To cite this abstract:Eva Mørtsell, Sigmund Andersen, Calin Marioara, Jostein Røyset, Jesper Friis, Randi Holmestad; Characterization of multicomponent Al alloys by TEM, HAADF-STEM, EELS and DFT. The 16th European Microscopy Congress, Lyon, France. https://emc-proceedings.com/abstract/characterization-of-multicomponent-al-alloys-by-tem-haadf-stem-eels-and-dft/. Accessed: December 12, 2018
EMC Abstracts - https://emc-proceedings.com/abstract/characterization-of-multicomponent-al-alloys-by-tem-haadf-stem-eels-and-dft/