Cryogenic formability and deformation behavior of 2060 Al–Li alloys with water-quenched and T4 aged temper

Abstract

In this study, the formability and deformation behavior of new third-generation aluminum-lithium alloys at temperatures ranging from 113 to 298 K were studied by uniaxial tension tests, Erichsen cupping tests, and microstructure observations. The results show that the water quenched 2060 alloy exhibits excellent formability at 113 K with a fracture elongation of 34.1%, and Erichsen cupping value of 10.1 mm that are 33.2% and 40.3% higher than those at 298 K. Homogeneous plastic deformation was obtained at the cryogenic temperature for the water quenched alloy, as was reflected by the following three observations: 1) homogeneous lattice rotation and fewer coarse slip bands occurred in the grains; 2) a large number of substructures (i.e., dislocation cells, subgrains) uniformly distributed in the interior grains; 3) serrated flow caused by the dynamic strain aging disappeared at the cryogenic temperature. The naturally aged 2060 alloy exhibited limited formability improvement. As temperature decreased from 298 K to 113 K, the fracture elongation increased slightly by 11.8% and the Erichsen cupping value decreased by 26.4% for the naturally aged Al–Li alloy. The δ' precipitation phase of the naturally aged Al–Li alloy gave rise to planar slip due to the low misfit with the Al matrix and induced stress concentration at the grain boundaries. Meanwhile, the planar slip resulted in a higher texture and anisotropy at the cryogenic temperature, triggering early fracture and decreasing the ductility.