Influence of minor Sc on microstructure and properties of AA7085 alloy

The age-hardening response, mechanical, and corrosion-resistant properties of AA7085 alloys with and without the addition of 0.3 wt.% scandium (Sc) were compared. Using advanced techniques such as aberration-corrected transmission electron microscopy and first-principles calculations, the underlying micromechanisms of Sc microalloying were revealed. Results show that the increase in strength of the AA7085-Sc alloy is mainly attributed to the decreased Al grain size and increased number density of both Al 3 Sc@Al 3 (Sc,Zr) core-shell nanoparticles and Sc-containing η p and GP- η p nanoprecipitates. Strong strain fields and evident electron transfer from Zr to the neighboring matrix Al atoms exist at the Al 3 Sc@Al 3 (Sc,Zr)/Al interface. The Sc doping in GP- η p and η p suppresses the GP- η p → η p transformation. Modified corrosion resistance of the AA7085-Sc alloy compared with AA7085 alloy is associated with the fine grain boundary precipitates of η phases and narrow precipitation free zone. The reasons of property changes of AA7085 alloy after Sc microalloying are explored based on the multiscale microstructural characterization.