Interfacial tuning for the nucleation of liquid AlCu alloy

Heterogeneous nucleation interface structure of Al-Cu alloys was tuned through solute composition and substrate lattice structure in this study to achieve a sophisticated nucleation control. The tuning mechanism at atomic level was systematically investigated using high angle annular dark field scanning transmission electron microscopy (HAADF STEM) and electron energy loss spectroscopy (EELs) techniques. The results show that the solutal element and substrate both can be used to modify the lattice matching of the nucleation interface, where alloying element Cu was found to adsorb at the nucleation interface tuning the lattice matching between new crystal and substrate rather than embed in the matrix distorting the lattice structure of the matrix. The substrate structure can also affect the preferred crystal orientation of new crystals instead. A relationship between the nucleation potency (undercooling) of the alloys and the lattice misfit was further proved, which may lead to a quantitative approach for the nucleation control of Al.

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