Study on the influence of pre-stretching degree on the strength and microstructure evolution of an Al-Cu-Li alloy

Abstract

Abstract Al-Li alloys can be strengthened by pre-stretching before artificial aging to promote the precipitation of the strengthened phase. This study investigates the mechanical properties and evolution of a 2 mm thick Al-Cu-Li alloy sheet’s microstructure with various pre-stretching degrees. From the results, as the degree of pre-stretching is increased, the strength gradually increases. Particularly noticeable is the upward trend in yield strength. By the pre-stretching volume of 4%, tensile strength can be enhanced by 95 MPa and yield strength by 187 MPa. Pre-stretching leads to a gradual reduction in precipitation of θ′, an increase in T1 phase number density but a reduction in T1 phase diameter. Meanwhile, a combination of strain-hardening and precipitation-strengthening determines the yield strength. Increasing the pre-stretching degree increases strain-hardening, while T1 phase strengthening decreases gradually.