Effect of Rolling Temperature on Annealing of aa1050 Aluminium Alloy

Abstract

Commercially pure, dilute aluminium alloys, such as AA1050, dynamically generate sub-grains during cold rolling. If AA1050 is rolled at cryogenic temperatures (liquid nitrogen), this large decrease in temperature minimises the occurrence of dynamic recovery during rolling. The result is that the material has a large amount of stored energy and a high dislocation density, thereby giving it a high strength. This research looks at the recovery and recrystallization processes during annealing after cryo-rolling, and compares the formation of sub-grains and recrystallized grains to those where rolling was performed at room temperature. The type of dislocation structure that forms during the rolling process directly affects the evolution of the microstructure post-deformation. Owing to the extreme temperatures of cryo-rolling, the dislocation structure cannot undergo dynamic recovery. Instead, a distinct cell-like structure forms, with dense dislocation walls that are high energy. During subsequent annealing, the driving force for recrystallization is increased with a decrease in the rolling temperature, with the cryo-rolled material having a greater number of nucleation seed and consequently, a fine grained recrystallized microstructure.