Effect of Zn Content on the Mechanical Properties, Damping Capacity, and Intergranular Corrosion of Al-Mg-Zn-Sc Alloys

Hot rolling, cold rolling, solution treatment-natural aging, and solution treatment-artificial aging were used to process Al-7 Mg-xZn-0.25Sc alloys (x = 0, 1wt.%, 2wt.%, and 3wt.%). The grain size of these alloys after deformation or heat treatment decreased with increased Zn. Dynamic and static precipitations of T′/T occurred in the alloys with Zn content during deformation and heat treatment, respectively, and the volume fraction of the precipitated phases in the Al-7 Mg-xZn-0.25Sc alloys increased with increased Zn content. The strength of the alloys also increased with increased Zn content at all states, and the yield strength and ultimate tensile strength of the alloy with 3% Zn content after cold rolling reached 403 and 567 MPa, respectively. Compared with the rolled alloys, the heat-treated alloys exhibited much higher ductility due to their higher numbers of Mg solution atoms, and the elongation of all T4 alloys exceeded 30%. The lack of pinning points for the movable dislocations and the high-volume fraction of T phases caused the high Zn content alloy after hot rolling to exhibit higher room-temperature internal friction values than the other alloys. However, the high-Zn concentration Al-7 Mg-xZn-0.25Sc alloy exhibited weak corrosion resistance due to the formation of T grain boundary phases, which increased the electrochemical imbalance.