Improvement in the mechanical properties and creep resistance of Al-Mn-Mg 3004 alloy with Sc and Zr addition

Sc and Zr were added to Al-Mn-Mg 3004 alloy to form two populations of strengthening particles (50-70 nm-sized α-Al(Mn,Fe)Si dispersoids and 6-8 nm-sized Al3(Sc,Zr) precipitates), and their strengthening effects on the mechanical properties and creep resistance at ambient and elevated temperatures were studied. The results showed that the microhardness and yield strength at ambient temperature greatly increased upon the addition of Sc and Zr. The creep resistance at 300 °C significantly improved due to the precipitation of fine Al3(Sc,Zr) particles and reduction of the particle-free zone. However, the yield strength at 300 °C remained constant even though the Sc and Zr content increased. The combined effects of α-Al(Mn,Fe)Si dispersoids and Al3(Sc,Zr) precipitates on the yield strengths at 25 °C and 300 °C were quantitatively analyzed based on the Orowan bypass and dislocation climb mechanisms. The analytically predicted yield strengths are in good agreement with the experimental data.