Stabilization of ultrafine-grained structure in AA2219 alloy during high-temperature equal-channel angular pressing to an exceptional cumulative strain

This study investigates the microstructural stability of a commercial AA2219 Al-Cu alloy during equal-channel angular pressing (ECAP) at 300°C to an exceptionally high cumulative strain of e =16. Building upon previous work that revealed accelerated grain refinement up to strain e = 8 attributed to dispersoids, the current findings show that further deformation to e =16 exhibits a distinct tendency towards saturation of the microstructural evolution. The saturation is manifested in the asymptotic approach of key microstructural parameters to steady-state values. The ultrafine-grained structure stabilizes with an average fine grain size of ≈2.4 – 2.5 μm, a high-angle boundary fraction of 64 – 66 %, a volume fraction of new refined regions (coarse grain remnants excluded) of ≈84.5 %, and the development of a stable, intense shear texture dominated by {111}〈110〉 and {112}〈110〉 components. Comprehensive microstructural analysis via electron backscatter diffraction and transmission electron microscopy confirms that the fine, thermally stable dispersoids (e. g., aluminides of Zr, Mn, and Cr) effectively pin boundaries and dislocations, suppressing significant grain growth, boundary migration, and further lattice rotation. These results highlight the achievable microstructural and textural stability in dispersion-strengthened aluminum alloys under prolonged severe plastic deformation, which is important for applications requiring thermally stable fine-grained materials.

1. The research was supported by the Ministry of Science and Higher Education of the Russian Federation within the framework of the state assignment of IMSP RAS - № 124022900107-6