High resolution transmission electron microscopy study on the development of nanostructured precipitates in Al–Cu obtained by mechanical alloying

Aluminum alloy 2014 is used to obtain nanostructured powders via mechanical alloying. The evolution of the diffusion processes is observed by the development of defect structures and nanoprecipitates after 10 h of milling. The characterization includes analytical and high resolution transmission electron microscopy. Dislocations associated with different Al/Cu ratio affect the material. These defects act as nucleation sites where precipitates of the ɛAl2Cu3 hexagonal phase have been identified. Moiré fringes show the interference of {1 1 1}Al with {1 0 −1 0}εAl2Cu3 glide planes and locally small shifts of 1/3{1 1 1}Al and 1/3{1 0 −1 0}εAl2Cu3. Changes in the Al/Cu ratio lead to the formation of other solid solutions identified in the Cu rich area and could correspond to transition phases.

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► Development of defect structures and nanoprecipitates after 10 h of mechanical alloying in Al–Cu system.
► Defects act as nucleation sites of the ɛAl2Cu3 phase.
► Incoherent and semicoherent precipitates are identified by TEM–HRTEM.
► Moiré patterns are associated to the ɛAl2Cu3 phase.