Effect of Scandium on the Interaction of Concurrent Precipitation and Recrystallization in Commercial AA3003 Aluminum Alloy

In the current study, the effect of Sc addition on the interaction of concurrent precipitation and recrystallization in commercial AA3003 aluminum alloy was investigated using optical microscopy, scanning electron microscopy, and transmission electron microscopy. In case of AA3003 alloy, which was cold rolled to a true strain of 2.20 and heated at a heating rate of 150 K/s, the onset of precipitation and ending of recrystallization are signified by the critical temperature, T _C ~740 K (467 °C). There is a change in the shape of the recrystallized grains from pancake-like to equiaxed shape, as the annealing temperature increases greater than T _C. In case of AA3003 alloy microalloyed with 0.4 wt pct of Sc, the high no. density precipitation of coherent Al₃Sc precipitates always occurs before recrystallization because of the small nucleation barrier and high rate of decomposition. This leads to extremely coarse pancake-like recrystallization grains with high fraction of low-angle grain boundaries in the entire annealing temperature range, even at a high brazing temperature of 883 K (610 °C).