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Appl. Sci. 2018, 8(10), 1741; https://doi.org/10.3390/app8101741

Study on Microstructure and Fatigue Damage Mechanism of 6082 Aluminum Alloy T-Type Metal Inert Gas (MIG) Welded Joint

1
School of Materials Engineering, Shanghai University of Engineering Science, Shanghai 201620, China
2
Shanghai Collaborative Innovation Center of Laser Advanced Manufacturing Technology, 333 Long Teng Road, Shanghai 201620, China
*
Author to whom correspondence should be addressed.
Received: 10 September 2018 / Revised: 19 September 2018 / Accepted: 20 September 2018 / Published: 27 September 2018
(This article belongs to the Special Issue Selected Papers from the NMJ2018)
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Abstract

In this experiment, the T-joint of a 6082 aluminum alloy was welded by metal inert gas (MIG) welding and a fatigue test was carried out at room temperature. The mechanisms of generating pores and of fatigue fracture in welded joints are revealed in the case of incomplete penetration. There are two main types of pores: pores that are not welded and pores that are near the upper weld line of the weld. During welding, bubbles in the molten pool are adsorbed on the surface oxide film that is not penetrated, and cannot be floated to form pores; since it is a T-shaped welded joint, the molten pool is overhanged during welding, thereby forming pores near the fusion line. The fatigue strength of the welded joint based on the S–N curve at 107 cycles is estimated to be 37.6 MPa, which can reliably be predicted in engineering applications. Fatigue tests show that fatigue cracks are all generated in the pores of the incomplete penetration, and it and the pores form a long precrack, which leads to large stress concentration, and the fracture occurs under a small applied load. Grain morphology around the pores also has a large effect on the fatigue properties of the T-weld joint. In the weld’s fatigue fracture, it was found that the crack stable-extension zone exhibited ductile-fracture characteristics, and the instantaneous fault zone is composed of a large number of tear-type dimples showing ductile fractures. View Full-Text
Keywords: aluminum alloy; MIG; T-joint; pore; fatigue damage mechanism aluminum alloy; MIG; T-joint; pore; fatigue damage mechanism
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Duan, C.; Yang, S.; Gu, J.; Xiong, Q.; Wang, Y. Study on Microstructure and Fatigue Damage Mechanism of 6082 Aluminum Alloy T-Type Metal Inert Gas (MIG) Welded Joint. Appl. Sci. 2018, 8, 1741.

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