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Effect of Friction Stir Welding on the Micro-Structure and Mechanical Properties of Al-Cu Bilayer Sheets Produced by Roll Welding

Beygi, Reza | 2014

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 46040 (07)
  4. University: Sharif University of Technology
  5. Department: Materials science and engineering
  6. Advisor(s): Kokabi, Amir Hossein; Kazeminezhad, Mohsen
  7. Abstract:
  8. Nowadays, bilayer sheets are increasingly used in various industries due to high mechanical properties, high corrosion resistance and low weight. Hence, it seems important to investigate welding of these materials. The main object of this study is to investigate mechanical properties and microstructure of friction stir butt welded Al-Cu bilayer sheets. For this purpose, tensile tests, microhardness measurements, metallographic images, SEM, EDS and XRD analyses have been carried out from the joints. The results show that contact condition between the shoulder and bilayer material (slipping or sticking), plays an important role in material flow during welding and weld quality. Also the geometry of shoulder is so critical. When Al is in contact with the shoulder, sticking condition is developed, while Cu is more likely to develop slipping contact condition. This results in sound joint formation by welding from Cu side and using the flat shoulder. While by welding from Al side, it is essential to use concave shoulder. The mechanical properties of the joints depend on defects, intermetallic formation and dispersion of these compounds in the joint. Generally, the amount of intermetallic compounds during welding from Cu side are more than that of Al side. Also the amount of mixing in the advancing side of the weld is more than that of the retreating side. The results of present study, can give a good insight into understanding of material flow and weld quality during friction stir welding of bilayer sheets
  9. Keywords:
  10. Mechanical Properties ; Microstructure ; Friction Stir Welding ; Aluminum-Cupper Bilayer Sheet ; Contact Condition

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