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Microstructure Development during Low-Current Resistance Spot Welding of Aluminum to Magnesium

1
Faculty of Engineering and Informatics, University of Bradford, Richmond Road, West Yorkshire BD7 1DP, UK
2
Mechanical Engineering Department, University of Technology, Jamaica, 237 Old Hope Road, Kingston 6, Jamaica
*
Author to whom correspondence should be addressed.
J. Manuf. Mater. Process. 2019, 3(2), 46; https://doi.org/10.3390/jmmp3020046
Received: 9 May 2019 / Revised: 11 June 2019 / Accepted: 12 June 2019 / Published: 14 June 2019
Resistance spot welding of aluminum (Al5754) to magnesium (AZ31B) alloys results in the formation of a variety of solidification microstructures and intermetallic compounds that may affect the in-service performance of the weld. This study evaluates the relationship between the welding parameters and the properties of the weld nugget that is formed, and clarifies the morphological and microstructural evolutions within the weld regions during the low-current “small-scale” resistance spot welding of Al5754 to AZ31B. The investigations included a combination of microstructural characterization and thermodynamic analysis of the weld region. The results show that the welding time and clamping force parameters have significant effects on the properties of the nugget formed. The optimal welding parameters were found to be 300 ms welding time and 800 N clamping force. Weld nuggets formed with lower welding time and clamping force were undersized and contained extensive porosity. Meanwhile, a clamping force above 800 N caused gross deformation of the test samples and the expulsion of the molten metal during the welding process. The most significant microstructural changes occurred at the weld/base metal interfaces due to the formation of Al17Mg12 and MgAl2O4 intermetallic compounds as well as significant compositional variation across the weld pool. The thermal gradient across the weld pool facilitated the formation of several microstructural transitions between equiaxed and columnar dendrites. View Full-Text
Keywords: resistance spot welding; dissimilar welding; equiaxed grains; columnar grains resistance spot welding; dissimilar welding; equiaxed grains; columnar grains
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Cooke, K.O.; Khan, T.I. Microstructure Development during Low-Current Resistance Spot Welding of Aluminum to Magnesium. J. Manuf. Mater. Process. 2019, 3, 46.

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