Abstract
The Cu interactions with the Al–Mg–Si alloy main hardening phase β″ are investigated in atomic scale, by using experimental and simulated high angle annular dark-field scanning transmission electron microscopy techniques and density functional theory calculations. Cu is located at or near the β″/Al interface, with the misfit dislocations normally observed for a precipitate of this size being absent. It is proposed that the small Cu volume is crucial to this mechanism. Present supercell based calculations cannot fully model these interactions.