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

Abstract

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.