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Materials 2017, 10(5), 449; doi:10.3390/ma10050449

Microstructure and Mechanical Properties of an Ultrasonic Spot Welded Aluminum Alloy: The Effect of Welding Energy

1,2
,
2,* and 3,4,*
1
College of Engineering and Technology, Southwest University, Tiansheng Road 2, Beibei District, Chongqing 400715, China
2
Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, ON M5B 2K3, Canada
3
Faculty of Materials and Energy, Southwest University, Tiansheng Road 2, Beibei District, Chongqing 400715, China
4
Advanced Materials Research Center, Chongqing Academy of Science and Technology, Yangliu Road 2, Chongqing 401123, China
*
Authors to whom correspondence should be addressed.
Academic Editor: Mark T. Whittaker
Received: 19 March 2017 / Revised: 15 April 2017 / Accepted: 21 April 2017 / Published: 25 April 2017
(This article belongs to the Section Manufacturing Processes and Systems)
View Full-Text   |   Download PDF [15002 KB, uploaded 25 April 2017]   |  

Abstract

The aim of this study is to evaluate the microstructures, tensile lap shear strength, and fatigue resistance of 6022-T43 aluminum alloy joints welded via a solid-state welding technique–ultrasonic spot welding (USW)–at different energy levels. An ultra-fine necklace-like equiaxed grain structure is observed along the weld line due to the occurrence of dynamic crystallization, with smaller grain sizes at lower levels of welding energy. The tensile lap shear strength, failure energy, and critical stress intensity of the welded joints first increase, reach their maximum values, and then decrease with increasing welding energy. The tensile lap shear failure mode changes from interfacial fracture at lower energy levels, to nugget pull-out at intermediate optimal energy levels, and to transverse through-thickness (TTT) crack growth at higher energy levels. The fatigue life is longer for the joints welded at an energy of 1400 J than 2000 J at higher cyclic loading levels. The fatigue failure mode changes from nugget pull-out to TTT crack growth with decreasing cyclic loading for the joints welded at 1400 J, while TTT crack growth mode remains at all cyclic loading levels for the joints welded at 2000 J. Fatigue crack basically initiates from the nugget edge, and propagates with “river-flow” patterns and characteristic fatigue striations. View Full-Text
Keywords: aluminum alloy; ultrasonic spot welding; EBSD; microstructure; tensile strength; fatigue aluminum alloy; ultrasonic spot welding; EBSD; microstructure; tensile strength; fatigue
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Peng, H.; Chen, D.; Jiang, X. Microstructure and Mechanical Properties of an Ultrasonic Spot Welded Aluminum Alloy: The Effect of Welding Energy. Materials 2017, 10, 449.

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