Mechanical properties improvement of the hybrid structures made by friction stir welding (FSW) of AA2198 and AA2024 materials is the goal of this research. Different tool designs, welding speed parameters, base metal heat treatment (T8 and T3) and post weld heat treatment (PWHT) were investigated in order to improve the mechanical properties of the joint. The tapered cylindrical pin with a raised fan shoulder was the optimal tool design configuration in terms of yield strength and elongation. A range of welding speed parameters was subsequently studied for the optimum tool design to find appropriate welding conditions. The joint efficiency can reach up to 78% by choosing optimum welding speed parameters of 750 RPM and 450 mm.min-1. It is observed that employing the plates in T3 or T8 will create joints with similar mechanical properties due to loss of mechanical properties in TMAZ/HAZ of AA2198 side. T8 PWHT with and without pre-straining was applied on welded samples in T3 conditions to recover the mechanical properties of joint areas. Both T8 PWHT process improved the hardness of TMAZ/HAZ of AA2198 side while they have not positive effect on TMAZ/HAZ of AA2024 side and the final mechanical properties did not improve. It can be concluded that T8 PWHT is not effective for the AA2024-AA2198 dissimilar joint. Besides, the temperature distribution of workpiece was achieved through FEM simulation. The simulation shows that cooling during welding could be effective for improving the joint mechanical properties by decreasing peak temperature and heat exposure time.
| Date | 25 Aug 2017 |
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| Original language | American English |
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| Awarding Institution | - École de technologie supérieure
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| Supervisor | Philippe Bocher (Supervisor) & Mohammad Jahazi (Co-supervisor) |
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Masoumi Khalilabad, M. (Author),
Bocher (Supervisor) &
Jahazi (Co-supervisor),
25 Aug 2017Student thesis: Master's thesis › Master in Engineering: Mechanical Engineering