Microstructure and Mechanical Properties of 5356 Aluminum Alloy Fabricated by TIG Arc Additive Manufacturing
SUN Jiaxiao1, YANG Ke1(), WANG Qiuyu1, JI Shanlin1, BAO Yefeng1, PAN Jie2
1.College of Mechanical and Electronic Engineering, Hohai University, Changzhou 213022, China 2.Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
Cite this article:
SUN Jiaxiao, YANG Ke, WANG Qiuyu, JI Shanlin, BAO Yefeng, PAN Jie. Microstructure and Mechanical Properties of 5356 Aluminum Alloy Fabricated by TIG Arc Additive Manufacturing. Acta Metall Sin, 2021, 57(5): 665-674.
5356 aluminum alloy has been widely applied in transportation, aerospace and other fields owing to its low density, excellent fatigue property, and superior corrosion resistance. Aluminum alloy is widely manufactured by the arc additive technique that operates at a fast manufacturing speed with simple equipment and high material utilization. The property of 5356 aluminum alloy is closely related to its microstructure. To better control the property of this alloy for the additive manufacturing of forming parts, it is necessary to study the evolution of its microstructure. In this work, 5356 aluminum alloy forming parts were produced by tungsten inert gas welding (TIG) arc additive manufacturing, and their microstructures and mechanical properties were analyzed. The 5356 aluminum alloy formed by TIG additive manufacturing was composed of α-Al matrix and β(Al3Mg2) phase. As the deposition height increased, the layer microstructure transformed from equiaxed grains to columnar grains and tended to stabilize at thermal equilibrium. The top layer exhibited a dendritic microstructure with serious segregation of the Mg element. The middle and lower microstructures were varied and included equiaxed grains, columnar grains, and a mixture of these, with improved Mg-element segregation. As the deposition height increased, the microhardness in the layer first decreased and then stabilized. The microhardness was larger in the interlayers than in the deposition layers. The pores gathered in the interlayers might explain the lower yield strength of the thin-walled parts than the theoretically calculated value. The tensile strength, yield strength, and elongation were all anisotropic, and the tensile property was better in the transverse than in the longitudinal direction. This result was attributable to pore accumulation between the layers of the thin-walled parts and to the uneven microstructure.
Fund: National Key Research and Development Program of China(2017YFE0100100);Changzhou Key Research and Development Plan (Social Development Science and Technology Support)(CE-20205046)
About author: YANG Ke, professor, Tel: (0519)85192035, E-mail: yangke_hhuc@126.com
Table 1 Chemical compositions of ER5356 welding wire, AA6061 substrate, and WAAM 5356 aluminum alloy
Fig.1 Schematic of WAAM 5356 aluminum alloy thin-walled parts preparation process and sample interception (a) and tensile specimen geometry (b)
Fig.2 OM images of microstructure of WAAM 5356 aluminum alloy thin-walled part from the 1st layer to the 12th layer (a-l), respectively
Fig.3 Grain areas of different deposited layers of WAAM 5356 aluminum alloy thin-walled part
Fig.4 OM image of microstructure of the 15th layer of WAAM 5356 aluminum alloy thin-walled part (I—area between layers, II—area within the layers)
Fig.5 Macrostructure and microstructures of top region of the WAAM 5356 aluminum alloy thin-walled part
Fig.6 XRD spectrum of WAAM 5356 aluminum alloy specimen
Fig.7 SEM (a) and OM (b) images of the WAAM 5356 aluminum alloy thin-walled part inner layers sample, and EDS of positions 1 (c) and 2 (d) in Fig.7a (c—atomic fraction)
Fig.8 Microhardness of the WAAM 5356 aluminum alloy thin-walled part inner layers
Fig.9 Microhardness of the WAAM 5356 aluminum alloy thin-walled part inter layers
Fig.10 Transverse and longitudinal yield strengths and theoretical yield strengths of WAAM 5356 aluminum alloy thin-walled part tensile samples (σys—yield strength, d—average grain diameter)
Fig.11 SEM images of the transverse (a) and longitudinal (b) tensile fracture morphologies (Insets show the enlarged views)
Specimen
Ultimate strength
MPa
Yield strength
MPa
Elongation
%
Transverse
276.7
133.2
29.8
Longitudinal
265.5
120.6
27.6
Table 2 Tensile test results
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