Achieving high strength and ductility of Al-Cu-Li alloy via creep aging treatment with different pre-strain levels. (December 2021)

• Record Type: Journal Article
• Authors: Yang, Xinghai; Wang, Junsheng; Zhang, Mingshan; Zhang, Chi; Xue, Chengpeng; Guo, Yueling; Liu, Xiaoguang
• Is Part Of: Materials today communications. Volume 29(2021)
• Publication Date: 2021-12
• Subjects: Al-Li alloys -- Creep aging -- Precipitation -- Heterogeneous nucleation -- Mechanical properties; Materials science -- Periodicals; 620.11
• DOI: 10.1016/j.mtcomm.2021.102898
• Languages: English
• ISSNs: 2352-4928

Abstract

Abstract: A method of integrating creep aging and pre-strain has been developed to optimize the strength and promote the nano-precipitates in an Al-Cu-Li alloy. The creep deformation, mechanical properties, and microstructure evolution of the alloy in different states were systematically investigated. The results show that creep aging at 200 ℃ with 9% pre-strain for 7 h can significantly increase the yield tensile strength (YTS) and ultimate tensile strength (UTS) to 604 MPa and 614 MPa, respectively, while maintaining the elongation greater than 8%. Due to the synergetic effect of creep aging and pre-strain, the main strengthening phase in the aged alloy is T1 phase. Pre-strains at5–9% accelerate the precipitation kinetics of T1 phase and significantly inhibits the precipitation of θ′ phase which is usually composited by a thin layer of δ′ phase. The length of T1 precipitate decreases with the pre-strain, but the thickness shows an opposite trend. The effects of pre-strain and dispersoid on promoting the heterogeneous nucleation of T1 phase were discussed. The strengthening mechanisms after creep aging with pre-strains are mainly ascribed to the effects of strain strengthening and precipitation strengthening, which were further quantitatively analyzed. Graphical Abstract: ga1 Highlights: The yield strength of Al-Cu-Li alloys can increase up to over 600 MPa by creep aging at 200 ℃ for 7 h. The size for strengthening nano T1 phase can be significantly refined by creep aging after pre-straining. Nucleation of θ′ phases can be suppressed by creep aging with pre-straining. Al20 Cu2 Mn3 dispersoids accelerate the heterogeneous nucleation of T1 phase.