Effect of Pretreatment and Cryogenic Temperatures on Mechanical Properties and Microstructure of Al-Cu-Li Alloy

Abstract

The mechanical properties of Al-Cu-Li alloys after different pretreatments were investigated through tensile testing at 25 and −196 °C, and the corresponding microstructure characteristics were obtained through optical metallography, scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy. An increasing mechanism of both strength and ductility at cryogenic temperatures was revealed. The results show that the hot deformation pretreatment before homogenization promoted the precipitation of Al3Zr particles, improved particle distribution, and inhibited local precipitation-free zones (PFZ). Both hot deformation pretreatment before homogenization and cryogenic temperature were able to improve strength and ductility. The former improved strength by promoting the precipitation of Al3Zr particles while enhancing the strengthening effect of the second-phase particles and reducing the thickness of the coarse-grained layer. Meanwhile, the increase in ductility is attributable to the decrease in thickness of the coarse-grained layer, which reduced the deformation incompatibility between the coarse and fine grains and increased the strain-hardening index. The latter improved the strength by suppressing dynamic recovery during the deformation process, increasing the dislocation density, and enhancing the work hardening effect. Additionally, the increase in ductility is attributable to the suppression of planar slip and strengthening of grain boundaries, which promoted the deformation in grain interiors and made the deformation more uniform.

Effect of Al3Zr Dispersoid on Microstructure and Mechanical Properties of Al-Cu-Li Alloy During Composite Spinning-Extrusion Forming

“…This is attributed to Al 3 Zr pinning grain boundaries and inhibiting the growth of surface grains during static recrystallization. The effect of Al 3 Zr on reducing the coarse-grain layer thickness of Al-Cu-Li alloy has also been confirmed in another study on rolled plate by our research group (Wang et al, 2021).…”

“…In addition, its fine and continuous distribution can reduce the degree of recrystallization and improve mechanical properties (Tsivoulas and Robson, 2015). A 3 Zr dispersoids can effectively reduce the thickness of the coarse-grained layer, inhibit the local PFZ, and improve the properties of the Al-Cu-Li alloy (Wang et al, 2021). At present, there is no public report on the formation of Al 3 Zr dispersoids and CSE, and its coupling factors and mechanism still need to be further explored.…”

Effect of the Second Phases on Composite Spinning-Extrusion Forming and Mechanical Properties of Al–Cu–Li Alloy

“…The strengthening mechanism of Al-Cu-Li alloy included solid solution strengthening, fine crystal strengthening, second phases particle strengthening and work hardening [31]. Due to the same chemical composition, composite spinning-extrusion forming process, solution treatment and T8 heat treatment of the four samples, the strength difference at T8 were mainly due to the precipitation of aging strengthened phase and the contribution of grain refinement.…”

Influence of Cryogenic Temperatures on the Mechanical Properties and Microstructure of 2195-T8 Alloy

“…Numerous studies on aluminum alloys in cryogenic environments found that the strength of aluminum alloys increases with decreasing temperatures [5][6][7][8][9][10][11]. Wang et al [5] compressed 7A85 aluminum alloy forgings at room temperature and low temperatures, followed by solution treatment and aging.…”

“…In summary, although there have been many studies on aluminum alloys in cryogenic environments, these studies mainly focus on cryogenic plastic deformation processes [5][6][7][8][9][10][11]. The alloy states studied are mostly annealed, solution-treated, and homogenized, with less research being conducted on aging-state aluminum alloys.…”