Effects of deformation temperature on the evolution of second mechanical phase and properties of large 2219 Al-Cu alloy rings

Transition rings of 2219 Al-Cu alloy for tanks with diameters exceeding 5 m require superior mechanical properties. However, the coarsening and agglomeration of Al2Cu second-phase particles deteriorate the mechanical properties of large 2219 Al-Cu alloy rings manufactured by the conventional hot rolling process. An improved process, including warm rolling and cold compression, was performed for improving the mechanical properties of such rings. The results showed that warm rolling can facilitate the dispersion and fragmentation of Al2Cu particles and that cold compression can lead to a significant accumulation of dislocations, as compared with hot rolling. Dispersed Al2Cu particles were beneficial for uniform distribution of Cu in the Al matrix after heat treatment; fragmented Al2Cu particles were dissolved more sufficiently during heat treatment, with the assistance of a larger number of dislocations per unit volume. More uniform and higher Cu content in the Al matrix of the sample undergoing the improved process leads to a more uniform distribution, greater area fraction, and larger size of theta' phases, and improved yield strength. The elongations of the samples undergoing warm rolling increased significantly because of the positive change of fracture behavior owing to refinement of Al2Cu particles.