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On the Microstructure and Mechanical Properties of Aluminum after Low-temperature Multi-directional Forging

Alyani, Ali | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51817 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Kazeminezhad, Mohsen
  7. Abstract:
  8. Severe Plastic Deformation (SPD) has been used as an effective approach to access fine grain (FG) and ultra-fine grain (UFG) materials.the Temperature of SPD is a dominant parameter to controlling ultimate properties. SPD at room-temperature and the high temperature was used widely in literature but the low-temperature process (sub-zero and cryogenic temperatures) was not used comparably. In this study, Low-temperature Multi-Directional Forging (LMDF) was applied on commercially pure aluminum and room-temperature MDF (RMDF) was attained for contrast temperature effects, and resulting in more fine grains. The grain refinement was attributed to the fragmentation process with a limitation in grain refinement. The effects of post-deformation annealing heat treatment were discussed. Evolutions of dislocations density during SPD were investigated using a physical-based model namely modified ETMB which considers cross-slip and climb process by adding a metallurgical term in conventional ETMB models. Furthermore, an annealing model with recovery stage was used in this study to show the flow stress behavior of multi-directionally forged aluminum after static recovery. A self-annealing behavior was detected in LMDF samples and an atypical grain growth after 365 days was observed and it was attributed to extensive-recovery process. Overall, it was found that low-temperature can suppress dynamic recovery partially and it can improve work-hardening capacity in comparison with room-temperature
  9. Keywords:
  10. Multidirectional Forging ; Low Temperature ; Aluminum ; Microstructure ; Mechanical Properties ; Severe Plastic Deformation

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