Effects of Mn content on recrystallization resistance of AA6082 aluminum alloys during post-deformation annealing

The microstructural evolutions under as-homogenized and as-deformed conditions and after the postdeformation annealing of AA6082 aluminum alloys with different Mn content (0.05 wt.%-1 wt.%) were studied by optical, scanning electron, and transmission electron microscopies. The results showed that the presence of a large amount of alpha-Al(Mn,Fe)Si dispersoids induced by Mn addition significantly improved the recrystallization resistance. In the base alloy free of Mn, static recrystallization occurred after 2 h of annealing, and grain growth commenced after 4 h of annealing, whereas in Mn-containing alloys, the recovered grain structure was well-retained after even 8 h of annealing. The alloy with 0.5% Mn exhibited the best recrystallization resistance, and a further increase of the Mn levels to 1% resulted in a gradual reduction of the recrystallization resistance, the reason for which was that recrystallization occurred only in the dispersoid-free zones (DFZs) and the increased DFZ fraction with Mn content led to an increase in the recrystallization fraction. The variation in the dispersoid number density and a coarsening of dispersoids during annealing have a limited influence on the static recrystallization in Mn-containing alloys. (C) 2020 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.