Effects of Warm Rolling Deformation on the Microstructure and Ductility of Large 2219 Al–Cu Alloy Rings

Large 2219 Al–Cu alloy transition rings are extensively utilised in launch vehicles. However, coarse-grained structures and agglomerated Al₂Cu second-phase particles considerably decrease the ductility of large 2219 Al–Cu alloy rings manufactured using the conventional hot rolling process. In this study, 10%–40% warm rolling deformation was applied to elucidate the evolution of grain structures, characteristics of the Al₂Cu second-phase particles, and the influencing mechanisms of ductility. The results indicate that increased warm rolling deformation can facilitate dynamic recrystallisation and yield more sub-grains, which leads to the appearance of numerous finer and more equiaxed recrystallised grains after solution heat treatment; however, the homogeneity of the grain structure is decreased. With increased warm rolling deformation, Al₂Cu second-phase particles are more dispersed and more completely fragmented; furthermore, the dispersed and fragmented Al₂Cu particles are more thoroughly dissolved during solution heat treatment. By the combined action of grain structures and second-phase particles, the main fracture mode transitions from intergranular fracture into transcrystalline fracture. This results in elongation in the axial and circumferential directions increasing steadily with increased warm rolling deformation; elongation in the radial direction initially increases, and finally decreases due to the appearance of glide planes. Samples that experience a warm rolling deformation of 30% exhibit the best overall elongation.