Development of ultra-high strength Al–Cu–Li alloys containing high Mg through the combination of pre-stretching and age-hardening

Precipitation strengthening and strain hardening after pre-deformation in low Mg Al–Cu–Li alloys dominated by T1 phases have been widely studied in recent years due to their excellent mechanical properties. In this study, the aging precipitation behavior and the associated strengthening mechanisms caused by the increasing dislocation density in high Mg Al–Cu–Li alloys were systematically studied. The results showed that the dislocation density change along with the degree of the pre-stretching as well as the precipitation behavior, that is the pre-stretched methods inhibit the development of GPB zones and reduce the total precipitation of T1 phases to promote the development of S phases. Finally, the fraction of recrystallized zones decreases from 59.3% to 2.8% while the average KAM value increases from 0.62 to 1.40, and the yield strength increases from 500 MPa to 620 MPa. The overall precipitation strengthening increment in the case of multi-phase coexistence is essentially independent of dislocation density, which is mainly a result of the decrease in the strengthening increment for T1 phases is compensated by the strengthening increment for S phases. Our study is expected to provide theoretical contributions to the development of high-strength and high-toughness Al–Cu–Li alloys.