Abstract

• Observation of copper-bearing precipitates evolution at atomic level. • Confirmation of the existence of β′′/Q′ composite precipitates. • Complete transformation of cooper-bearing phases into Guinier Preston zones during deformation. • Ultra-high strength and favorable conductive properties for new-generation aluminum alloy conductor. We modified the morphology and distribution of copper-bearing precipitates in an Al-Mg-Si-Cu alloy and obtained ultra-high comprehensive properties through a modified thermo-mechanical treatment composed of aging and cold deformation. The precipitate evolution and atomic structure was observed by employing atomic resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). Our results proved the existence of β′′/Q′ composite precipitates in rod-like morphology after aging treatment due to the inhibition of β′′ phase formation by copper atoms. We also revealed that the peak-aged phases transformed into in-situ reverse-transformed Guinier Preston zones (GP zones) during the deformation process. By the means of modifying the precipitates, we finally simultaneously obtained ultra-high strength (424.40 MPa) as well as favorable conductive properties (52.78%IACS), both of which surpassed three mainstream standards for high strength aluminum conductor.

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