Microstructure and Mechanical Properties of 2024 Aluminum Alloy Prepared by Wire Arc Additive Manufacturing
WU Dongjiang, LIU Dehua, ZHANG Ziao, ZHANG Yilun, NIU Fangyong, MA Guangyi()
State Key Laboratory of High-Performance Precision Manufacturing, Dalian University of Technology, Dalian 116024, China
Cite this article:
WU Dongjiang, LIU Dehua, ZHANG Ziao, ZHANG Yilun, NIU Fangyong, MA Guangyi. Microstructure and Mechanical Properties of 2024 Aluminum Alloy Prepared by Wire Arc Additive Manufacturing. Acta Metall Sin, 2023, 59(6): 767-776.
Owing to its outstanding advantages, such as low specific gravity, high specific strength, and good machinability, 2024 aluminum alloy has been used as various load components in the aerospace field and has become an important lightweight material. The properties of the 2024 aluminum alloy are highly correlated with its microstructures. Accordingly, in this study, 2024 aluminum alloy deposited specimens were fabricated using wire arc additive manufacturing. Further, the microstructures and mechanical properties of the deposited specimens were investigated in different regions. The layered characteristics could be observed macroscopically in the deposited specimens, and a single deposition layer was divided into two regions: interlayer and innerlayer. The grain morphology changed from equiaxed grains in the innerlayer region to columnar grains in the interlayer region. The deposited specimens mainly included α-Al, θ-Al2Cu, and S-Al2CuMg phases. In the nonequilibrium solidification process of additive manufacturing, the deposited specimens presented element segregation. The distribution of Mg in the Al matrix was uniform for the innerlayer region. However, Cu was segregated as eutectics at the grain boundary in the interlayer region. The average tensile strength, yield strength, and elongation of deposited specimens were (323.5 ± 6.6) MPa, (178.7 ± 6.2) MPa, and (9.03 ± 0.67)%, respectively, which were higher than those of cast annealing 2024 aluminum alloy. Owing to the difference in the microstructure, the innerlayer and interlayer regions showed different crack propagation behavior. The cracks in the interlayer region propagated along the distribution path of eutectics, showing intergranular fracture, and the crack propagation mode in the innerlayer region changed to transgranular fracture.
Table 1 Chemical compositions of 2024 wire and deposited specimen
Fig.1 Schematic of deposited process (TIG—tungsten inert gas) (a) and dimensions of tensile test specimen (unit: mm) (b) for WAAM 2024 aluminum alloy
Fig.2 Morphologies of WAAM 2024 aluminum alloy deposited specimen at different positions
Fig.3 EBSD analyses of WAAM 2024 aluminum alloy deposited specimen, paralleled to the building direction
Fig.4 Solidification pathways of Al-Cu-Mg alloy (a) and XRD spectra of 2024 aluminum alloy wire and WAAM deposited specimen (b) (Inset in Fig.4b shows the locally enlarged spectrum)
Fig.5 SEM image of WAAM 2024 aluminum alloy deposited specimen and EDS results of points P1 and P2 (a), line scanning of bright-white phase showed in the inset (b), and line scanning of gray phase showed in the inset (c)
Fig.6 SEM images of WAAM 2024 aluminum alloy deposited specimen
Fig.7 Element mapping of WAAM 2024 aluminum alloy deposited specimen
Fig.8 Microhardness distributions of WAAM 2024 aluminum alloy deposited specimen (a) and single layer (b) (Insets in Fig.8b show the microstructures in the innerlayer and interlayer regions)
Fig.9 Tensile curves of WAAM 2024 aluminum alloy deposited specimens under room temperature (a) and properties comparison of 2024 aluminum alloy prepared by different methods (b)
Fig.10 SEM images of fracture surface (a), SEM image and EDS of interlayer region (b), and SEM image and EDS of innerlayer region (c) of WAAM 2024 aluminum alloy tensile specimen (Figs.10a1 and a2 show the locally enlarged images in Fig.10a)
Fig.11 Crack propagation of tensile fracture of WAAM 2024 aluminum alloy tensile specimen
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