Cu segregation and symbiotic precipitation at the dispersoid/matrix interface in a Cd-microalloyed Al–Cu–Mn alloy

Manganese (Mn) generally is widely recognized for its effect on modifying the size and morphology of coarse Fe-rich constituents in Al-based alloys by forming fine Mn-rich dispersoids. However, this study suggests that in a Cd-micraolloyed Al-Cu-Mn-based alloy, Mn-rich dispersoids significantly promote Cu-rich precipitation at the interface during artificial aging (AA), leading to undesirable solute consumption of Cu and potential suppression of nanoprecipitation. With the help of atomic-resolution high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) and energy disperse spectroscopy (EDS), an interesting finding is that interfacial Cu segregation at the dispersoid/matrix interface can be assembled during natural aging (NA, approximately for ∼30 days) after quenching, consequently feeding the early-stage interfacial Cu-rich precipitation during AA. Intriguingly, the microalloying effect of Cd, as the fast diffuser, is highly possible to promotes this process, which is also simultaneously and increasingly collected by the dispersoids during AA. These findings are expected to provide new insights on microstructural architecture in multicomponent Al-Cu-based alloys, highlighting the synergistic effect between Cd microalloying and Mn-rich dispersoids.