Enhancement of recrystallization resistance of Al–Zr–Mn by two-step precipitation annealing

Al3Zr dispersoids formed during precipitation annealing can improve the recrystallization resistance of cold-rolled aluminium alloys. However, the dispersoids are often inhomogeneously distributed, and in areas where the dispersoid density is low the alloy may still be prone to recrystallization. In this work, two-step precipitation annealing sequences have been applied in order to study whether a denser dispersoid distribution can be obtained during such treatments than by applying the common procedure. The influence of the first annealing temperature was also studied by varying it in the range of 250–350 °C, while a final (second) holding temperature of 450 °C was applied in all experiments. After cold rolling to ɛ = 2.3 (90% thickness reduction) it was found that the highest recrystallization resistance was obtained by a two-step heat treatment, using a first annealing temperature of 250 °C. The higher resistance is most likely due to a denser and more homogeneous distribution of the Al3Zr dispersoids.