Friction Stir Technology of Advanced Metallic Alloys used for Structural Applications

  • Adesola O. Ajayi

Student thesis: Master's Thesis


The feasibility of applying Friction Stir Technology (FSW/P) to effectively join Nickel-based Superalloy materials is of aerospace importance. Friction Stir Welding/Processing (FSW/P) is a solid state joining process which utilizes heat to join materials of the same or different composition together. The study included the following phases, in consultation with Abu Dhabi Aircraft Technologies (ADAT): (i) FSW technique was carried out on three candidate materials; Inconel alloy 625, Inconel alloy 718 and Hastelloy X, and out of which alloy 718 was selected as the candidate material for further investigation as agreed with ADAT, (ii) a comprehensive FSW tool material selection and tool design was carried out by conducting pilot experiments to achieve sound quality welds, (iii) a special emphasis was put to develop better understanding of the interplay between welded material microstructure and mechanical properties to work towards optimizing the FSW process, and (iv) the microstructural analysis and the mechanical property data was used to carry out a comprehensive parametric study to develop a material specific friction stir welding window for the candidate material, that is, Inconel alloy 718. This study explains our findings and highlights the potential benefits offered by this advanced joining technique. The study revealed that alloy 718 can be friction-stir-welded having a high strength better than the base metal strength and a range of parameters exists where reasonably sound welds can be achieved without much change in microstructure of the material. Friction stir welded Inconel alloy 718 shows high microhardness and tensile profiles as compared to the Gas Tungsten Arc (GTA) welded material and in most cases it was found that pre- or post-heat treatments were not needed to homogenize the mechanical properties of welded material. Some recommendations for future work that could enable Mubadala Aerospace and ADAT to take steps towards benchmarking this novel technique were given.
Date of Award2014
Original languageAmerican English
SupervisorMohammad Omar (Supervisor)


  • Friction Stir Technology; Friction Stir Welding; Aerospace; Gas Tungsten Arc (GTA).

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