Influence of precompression deformation on the residual stress, microstructure, and mechanical properties of aluminum–lithium alloys

Abstract

In this study, quenched aluminum–lithium alloy specimens were subjected to precompression deformation (0 %–5 %). Then, the influence of predeformation amounts on the residual stress, microstructure, and mechanical properties of alloy specimens was investigated. Results revealed that the amount of residual stress release first increased and then decreased with increasing predeformation amount. The efficacy of residual stress release was influenced by the initial residual stress in the specimens and their mechanical properties at the surface and core. X-ray diffraction, electron backscatter diffraction, and transmission electron microscopy revealed that due to predeformation, more dislocations were retained in the matrix of the specimen. These dislocations provided nucleation sites for the formation of precipitates. The T1 phase content gradually increased with increasing predeformation amount, whereas the θˊ phase content first increased and then decreased. The contribution of microstructural evolution to the yield strength (YS) of specimens was further analyzed to elucidate the relation between the strengthening mechanism and microstructure. As the predeformation amount increased from 0 % to 2 %, the increase in YS was impacted by an increase in the dislocation density and the continuous precipitation of T1 and θˊ phases. When the predeformation amount was increased to 3 %–5 %, the YS of the specimen increased primarily due to T1 phase precipitation.