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An Investigation Into the Friction Stir Welding of Severely Plastic Deformed Aluminum Sheets

Sarkari Khorrami, Mahmoud | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42171 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Kokabi , Amir Hossein; Kazeminezhad, Mohsen
  7. Abstract:
  8. As aluminum sheets are used in transportation and aerospace industries, an increase in strength of these materials is important since with increasing of strength to weight ratio, energy and materials are saved. Recently, there are a lot of interests in ultrafine grained materials obtained using severe plastic deformation (SPD). The strength of material is increased while the shape and dimensions of material are not changed during SPD processes. Due to some limitations of SPD techniques, the ultrafine grained materials cannot be still made large enough for industrial applications; also it is difficult to directly manufacture a complex structure with an ultrafine microstructure. Therefore, the welding or joining of ultrafine grained materials has become very important. In addition, the joining of the parts together in order to produce engineering structures should be considered. There are many methods for imposing severe plastic deformation to the materials. In this study the commercial purity aluminum sheets are severely strained by 1 and 2 passes of constrained groove pressing (CGP) process at room temperature. The annealed, 1 and 2 passes CGPed specimens are then friction stir welded at different traveling and rotation speeds and the microstructure evolutions and mechanical properties of joints are investigated. It is observed that the traveling and rotation speeds have different effects on the mechanical properties of 1 pass CGPed specimen joints. Also, the initial strain values have an essential influence on the microstructure evolutions at stir and heat affected zones and mechanical properties of joints. In addition, it is revealed that in contrast to 1 pass specimens, 2 passes CGPed ones are entirely unstable upon FSW process. At last, the annealed and 2 passes CGPed samples are partial annealed after FSW process. The microstructure evolutions and mechanical properties of joints are examined after partial annealing.

  9. Keywords:
  10. Commercial Pure Aluminum ; Nanostructure ; Mechanical Properties ; Friction Stir Welding ; Severe Plastic Deformation

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