Effects of Zr and Sc additions on precipitation of α-Al(FeMn)Si dispersoids under various heat treatments in Al–Mg–Si AA6082 alloys

Abstract

Abstract The present work investigated the influence of Zr and Sc on the evolution of α-Al(FeMn)Si dispersoids (“α-dispersoids") in Al–Mg–Si alloys. Both the individual addition of Zr and the combined additions of Sc and Zr increased the size but decreased the number density of the α-dispersoids, indicating the reduction in the formation of α-dispersoids. However, the reduction levels were the most significant when heat-treated at 350 °C in the alloy with both Sc and Zr and at 400 °C in the alloy with only Zr, which were likely related to the different interactions between intermediate B’ precipitates and α-dispersoids with the addition of Zr and Sc. Although the α-dispersoids were suppressed in the Zr/Sc-containing alloys, their microhardness was generally higher than the base alloy, which can be attributed to the strengthening contribution induced by Zr and Sc either from their solid solution hardening or the precipitation hardening of Al3Zr/Al3(Sc, Zr) dispersoids.