Comparative study of Cd addition effects on precipitation in different aluminium alloys

This work demonstrates that Cd microadditions can enhance the precipitation of age-hardening precipitates in 2xxx and 6xxx alloys as well as the dispersoid precipitation in 3xxx alloys, but have a minimal effect on the precipitation in 7xxx alloys. Experimental and theoretical methods are utilised to investigate the nucleation and precipitation of precipitates/dispersoids in Cd-containing Al alloys. The enhanced precipitation of θ′ and α-dispersoids in 2xxx and 3xxx alloys, respectively, are proposed to result from the heterogeneous nucleation on earlier-formed Cd-rich nanoparticles, while the enhanced precipitation of β′′ in 6xxx alloys is attributed to the increased number density of effective Mg-Si co-clusters due to the Cd incorporation. This investigation provides theoretical basis for the design of precipitation-strengthened Al alloys via microalloying.