Enhanced strength and corrosion resistance of creep-aged AA2050 Al-Li alloy by pre-rolling deformation

Abstract

The influences of pre-rolling deformation (0–20 %) on the creep behavior, mechanical properties, corrosion behavior, and microstructures of solid solution AA2050 alloys were investigated during creep aging. The results show that the pre-rolling induced a large number of dislocations, which decreased the primary creep rate but increased the steady creep rate. As the pre-rolling strain increased from 0 % to 20 %, the peak-aged time of creep-aged alloys decreased from 40 h to 16 h, improving both yield strength (YS, from 474 MPa to 554 MPa) and ultimate tensile strength (UTS, from 522 MPa to 590 MPa). The elongation (EL) decreased from 11.2 % to 7.8 %. The strength enhancement originated from inhibited oriented precipitation effect, dislocation density increment, and dense T1 phases precipitation. Meanwhile, the area fraction of corrosion pits (fpits), intergranular corrosion (IGC) depth and stress corrosion cracking (SCC) susceptibility index (ISSRT) decreased from 7.13 %, 176 μm, and 6.1 % to 5.11 %, 33 μm, and 1.5 %, respectively. The increased resistances of pitting corrosion/IGC/SCC were attributed to the coarsening and Cu enrichment of grain boundary precipitates (GBPs), the formation of precipitation-free zones (PFZs) and low-angle grain boundaries (LAGBs), and the precipitation of T1 phases along dispersoids.