Effects of axial cold-compression on microstructure uniformity and mechanical property enhancement of large 2219 Al–Cu alloy rings

Abstract

2219 Al–Cu alloy transition rings with a diameter stretching 5 m require further enhancement to their comprehensive mechanical properties. However, currently applied warm rolling process can lead to an uneven grain structure, which notably causes the mechanical properties to become inferior in the radial direction. Thus, an axial cold-compression process (0–9%) was performed after warm rolling to improve the mechanical properties and reduce the anisotropies of such rings. The results indicated that on increasing the cold-compression deformation, the diameter of all the grains at each location decreased after heat treatment; this caused substantial elongations in all directions. Grain refinement by cold compression was more effective on the core than on the border; the 6% cold-compression samples exhibited maximum uniformity and minimum anisotropy of grain structures, resulting in the largest elongations in the radial direction. Numerous dislocations accumulate around the secondary-phase particles in the process of cold-compression, which expanded the diffusion range of Cu atoms during solution treatment; subsequently, the number and uniformity of θ′ phases increased, thereby causing the yield strength to increase in all directions. To sum up, cold-compression after warm rolling is feasible, with the 6% cold-compression sample exhibiting the most uniform microstructure and best mechanical properties.