Abstract:The microstructural evolution and mechanical properties of 2050 Al-Li alloy subjected to different rolling pre-strains (0-20%) and aging (T8) were studied. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to characterize the microstructure. The results show that the grains were significantly refined along the normal direction (ND) and the intragranular distortion increased with the increase of pre-strain level. The entanglement of defects, e.g., dislocations, provides a large number of nucleation sites for the precipitation of T₁ phases. This leads to larger number of precipitates and narrower distance between precipitates, thus improving the hindering effects on dislocation motions and the strength of the alloy. When the pre-deformation level reaches 16%, the alloy shows the highest density of T₁ phases and strength (the yield strength and tensile strength reach 568 and 584 MPa, respectively, and elongation is 8.6%). When the amount of pre-deformation is further increased to 20%, the atomic diffusion channels are reduced due to dislocation entanglement, and the reduction in the number of T₁ phases eventually leads to a decrease in strength of the alloy.

Key words: 2050 Al-Li alloy; rolling pre-deformation; T₁ phase; microstructure; mechanical properties