Recrystallization in a 6000-series automotive sheet alloy during solution heat treatment practice

This investigation follows the development of microstructure during recrystallization of AA6111, an automotive skin sheet alloy. The heating path through a commercial solution heat treatment line is simulated using electrical resistance heating at a rate of 20 degrees Cs-1, which represents the average heating rate through the recrystallization regime. The recrystallization kinetics are rapid, with the process occurring predominantly between 400 and 420 degrees C. The kinetics were followed through changes in recrystallization and deformation textures. These results indicated that the recrystallization kinetics were independent of grain orientation. A fine distribution of Q-phase inhibits an equilibrium grain shape from developing directly upon recrystallization, however, at temperatures above the recrystallization finish temperature of 430 degrees C dissolution of this phase removes the boundary pinning constraint and the grain morphology develops a more stable configuration.