Tribological and salt water corrosion behavior of dissimilar alloy welding using friction stir welding

• Main Author: Azman, Siti Harishah
• Format: Thesis
• Language: English; English
• Published: 2024
• Subjects: T Technology (General); TS Manufactures
• Online Access: http://eprints.utem.edu.my/id/eprint/28316/; https://plh.utem.edu.my/cgi-bin/koha/opac-detail.pl?biblionumber=124252

Friction stir welding (FSW) is a solid-state joining process that offers significant advantages in efficiency, cost-effectiveness, and environmental impact compared to traditional fusion welding techniques. This study focuses on the tribological and saltwater corrosion behavior of dissimilar aluminum alloy AA5052 and AA6061 welded joints produced using FSW, which are commonly used in marine applications due to their mechanical properties and corrosion resistance. The primary objective of this project was to comprehensively characterize the microstructure, mechanical properties, wear resistance, and corrosion behavior of dissimilar AA5052-AA6061 FSW joints. Various characterization techniques, including field-emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDX), tensile testing, microhardness mapping, reciprocating pin-on-disk wear tests, and linear sweep voltammetry (LSV), were employed to evaluate these properties. The results revealed that the dissimilar FSW joints exhibited unique microstructural developments along the bond line, leading to higher tensile strength and ductility compared to similar alloy joints. The tensile strength of the dissimilar joints was slightly higher, but they demonstrated lower wear resistance due to the formation of intermetallic compounds, such as Al3Mg2, at the weld interface. Corrosion testing indicated that the dissimilar joints had a lower overall corrosion rate but were susceptible to localized galvanic corrosion at the interface. This susceptibility was attributed to changes in composition and the formation of a passive oxide film, which dissolved at approximately -0.6V. The microstructural analysis showed significant differences between the similar and dissimilar joints. The similar AA6061 joints exhibited a uniform and defect-free surface with fine grains, whereas the dissimilar AA6061- AA5052 joints displayed distinct regions corresponding to each alloy with a well-bonded interface. The EDX analysis provided insights into the elemental distribution, revealing a gradual transition in composition across the weld interface for the dissimilar joints, indicating effective material mixing during the FSW process. The mechanical testing results highlighted the superior performance of the dissimilar joints in terms of tensile strength and ductility. However, the wear testing results indicated that the dissimilar joints had lower wear resistance compared to the similar joints, which could be attributed to the formation of intermetallic compounds at the weld interface. The corrosion testing using LSV showed that while the dissimilar joints had a lower overall corrosion rate, they were more susceptible to localized galvanic corrosion due to the differences in composition and the formation of a passive oxide film. This project provides critical insights into optimizing FSW parameters to mitigate corrosion challenges and enhance the mechanical performance of dissimilar aluminum alloy joints. The findings have significant implications for the development of lightweight, corrosion-resistant marine structures, contributing to improved reliability and durability in harsh marine environments. The insights gained from this research are expected to inform future advancements in the field, addressing both performance and durability in practical applications.