Investigation on the formability and deformation mechanism of aluminum alloy thin-walled parts at cryogenic temperature

Due to the poor ductility of aluminum alloy sheet at room temperature, which results in the difficulty in forming complex thin-walled parts, a novel forming method for thin-walled parts at cryogenic temperatures is proposed in this research, at which its strength and ductility are significantly improved. In this work, the cryogenic forming tests of the typical aluminum alloy thin-walled part were carried out, the formability and forming quality of the parts were evaluated, and the mechanism of the increase of strength-ductility at cryogenic temperature was discussed. The results of these experiments indicate that compared to room temperature, the formability of 2024-O aluminum alloy sheet at cryogenic temperature is significantly improved; the maximum forming height of aluminum alloy thin-walled part increases by 21.5% to 96 mm at − 180 ℃; in addition, the quality of parts formed at cryogenic temperature is better, whose maximum thinning rate is only half of the corresponding value at room temperature, and the hardness increases by 8.6%. It can be seen from the microstructure that when aluminum alloy deforming at low temperature, the dynamic recovery is restrained, the accumulation of dislocations leads to the increase of resistance to dislocation’s motion. The deformation of aluminum alloy at low temperature is more uniform, the work hardening ability is significantly improved, and its strength and ductility are enhanced. This study proves the feasibility of forming aluminum alloy thin-walled parts at cryogenic temperature, and provides a new idea for high-quality forming of complex thin-walled parts.