Influence of preliminary deformation on the hardening effect upon aging of Al–Cu–Li alloys

Resumo

The influence of preliminary deformation upon rolling of wedge specimens on the mechanical properties and the structural phase state of Al–Cu–Li alloys are studied by X-ray diffraction and hardness measurements. Strong dependence of the hardening effect upon aging on the reduction upon rolling has been revealed. Deformation weakly influences the hardness and significantly increases the hardening upon aging. Herewith, the hardening effect is nearly absent at the minimum deformation ratio of 1% and increases with its increase. It is demonstrated that the content of T₁ phase increases from 2 to 4% in the range of a preliminary deformation ratio of 6–10% and the content of δ' phase is ~17% at a deformation ratio in the range 1‒6% and increases to 18–19% at a deformation ratio of 6–10%. The δ' phase in an alloy contains <20% nanocrystalline particles with 6–20 nm in size, and the remaining part consists of amorphous particles (as detected by X-ray diffraction) <5 nm in size, which precipitate coherently from the matrix and have the same orientation as the nanocrystalline particles and the solid solution.