Cooperative Effect of Cryogenic Deformation and Artificial Aging on Microstructure and Mechanical Properties of 2219 Aluminum Alloy

doi:10.3901/JME.2025.14.063

Abstract

Abstract: Cryogenic forming has been developed into a kind of revolutionary forming technology for high-performance aluminum alloy thin-walled components. The mechanical properties and microstructure of heat-treatable strengthened aluminum alloy components that fabricated by cryogenic forming process are affected by cryogenic deformation and heat treatment. Therefore, the mechanical property evolution of 2219 aluminum alloy under the combined effects of cryogenic deformation and aging is systematically investigated through uniaxial tensile testing following cryogenic deformation and artificial aging. Additionally, the mechanism of precipitation is revealed through the characterization of grain structure and precipitated phases. The results show that cryogenic deformation significantly enhanced the mechanical properties and microstructure, which can be further optimized through appropriate artificial aging treatments. After cryogenic deformation, the strength of the 2219 aluminum alloy in W-temper increased significantly due to the multiplication and retention of dislocations and substructures. The yield strength of the specimens with 30% cryogenic deformation and natural aging reached 397.5 MPa, representing a 26.5% enhancement compared to the undeformed specimens, which exceeded the strength level of T87 temper. After artificial aging, the strengths under peak aging condition decreased with the increasing aging temperature; and the aging time of peak aging strength is shortened. The highest peak aging strength is obtained after aging at 150 ℃ for 18 h, with the yield strength reaching 408.9 MPa and the ultimate tensile strength reaching 488.4 MPa, respectively. Under this condition, the main strengthening phases are numerous diffusely distributed θ" phases. With the increase of aging temperature, the strengthening phases gradually transformed into θ′ phases. When the aging temperature is 200°C, the peak aging strength can be achieved by aging for 1 h, which can significantly shorten the manufacturing cycle. In addition, with the increase of artificial aging temperature, the high-energy microstructure retained by cryogenic deformation would recover, causing the decrease of yield strength and the increase of toughness. Therefore, excellent strength and toughness can be obtained simultaneity by cryogenic deformation and short-time high-temperature aging. In conclusion, excellent mechanical properties and microstructure can be obtained through reasonable matching of cryogenic deformation and artificial aging, providing theoretical guidance for regulation of mechanical properties and microstructure in cryogenic forming process of thin-walled structures.

Key words: aluminum alloy, cryogenic forming, artificial aging, mechanical properties, precipitation

CLC Number:

TG156

KANG Xin, YANG Guang, JIAO Jiao, ZHAO Zihao, FAN Xiaobo. Cooperative Effect of Cryogenic Deformation and Artificial Aging on Microstructure and Mechanical Properties of 2219 Aluminum Alloy[J]. Journal of Mechanical Engineering, 2025, 61(14): 63-72.

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