A Master of Science thesis in Mechanical Engineering by Emad Eldin Mohammed Kishta entitled, "Investigation of Submerged Friction Stir Welding of Marine-Grade Aluminum Alloy," submitted in January 2014. Thesis advisor is Dr. Basil Darras and thesis co-advisor Dr. Farid Abed. Available are both soft and hard copies of the thesis.
Friction stir welding is a newly developed welding technique utilized to weld lightweight alloys, such as aluminum alloys. Due to its low melting temperature, welding aluminum has been always challenging using conventional techniques. Friction stir welding can be controlled by different parameters like rotational speed, feed rate and welding medium. In this research, submerged friction stir welding of marine grade aluminum alloy 5083 is investigated. The study is divided into two parts, experimental and numerical investigations. In the experimental part, the effect of different welding parameters on thermal histories, tensile properties and microstructural properties are studied. The numerical part is a finite element modeling of the process to predict the changes in thermal profiles and material properties as the welding parameters are changed. The results of this study show that submerging highly affected the thermal histories and thus the microstructural and mechanical properties of the welded alloy. Controlling both the rotational speed and the feed rate found to be crucial to successfully friction stir weld aluminum and achieving good mechanical properties. The finite element model successfully predicted the thermal profile generated by friction stir welding under different parameters.