Effect of increased stretching deformation at cryogenic temperature on the precipitation behavior and mechanical properties of 2060 Al-Li alloy

A three-step process, which involved solution treatment, stretching deformation at cryogenic temperature, and artificial aging treatment, is a potential route to fabricate complex shaped thin-walled components of aluminum alloy. This study analyzed the influence of the cryogenic stretching deformation on subsequent aging behavior and mechanical properties of 2060 Al-Li alloy. The results showed that more dislocations accumulated in the sample with a larger deformation due to the suppressed dynamic recovery rate at low temperature, which provided more nucleation sites for the precipitation of T-1 phase, thus leading to a markedly homogeneous distribution. The increased number of T-1 phase consumed many copper atoms in aluminum matrix, which resulted in the decrease of the nucleation and growth rate of the theta ' phase. Optimized after-aging mechanical properties were obtained by increasing the stretching strain to 16%, with a yield strength of 538 MPa, an ultimate strength of 560 MPa, and a fracture elongation of 10.1%. The high strength resulted from the combination of precipitation strengthening and retained dislocation strengthening. The reason why the alloy still maintains a high ductility after being subjected to a larger stretching deformation was its high homogeneous deformation ability at cryogenic temperature. The further increase of the deformation resulted in the formation of defects, such as slip bands, and micro-cracks in the sample, leading to decreased after-aging ductility.