Effect of equal-channel angular pressing and post-aging on impact toughness of Al-Li alloys

Overcoming the toughness inadequacy of Al-Li alloys is in urgent need for developing new low-density and high-performance aerospace aluminum alloys. In this research, continuous equal-channel angular pressing (ECAP) and post-aging were developed to significantly enhance the impact toughness of 1420 Al-Li alloy. The effects of the processes on microstructure evolution, impact absorbed energy and fracture surfaces of 1420 alloy were investigated. The results demonstrated that the impact toughness of ultrafine-grained (UFG) 1420 alloy after 8 ECAP passes at 573 K reached up to 26.6 J/cm2 at room temperature and increased sixfold compared with that of the coarse-grained sample, but the post-aging reduced the beneficial effect. The remarkable improvement after the warm ECAP was mainly due to the UFG microstructure, certain amount of dislocations, and the fine precipitates with uniform distribution, thereby making UFG 1420 alloys more attractive in aerospace applications.