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Effect of Severe Plastic Deformation and Annealing on the Microstructure and Strength of Over-Aged AA 2024

Hosseini, Mohammad | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52943 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Kazeminezhad, Mohsen
  7. Abstract:
  8. Many researches have been done on the severe plastic deformation of 2024 aluminum alloy, but there is limited information on the effect of severe plastic deformation for this alloy in the over-aged condition. In this study, the effect of severe plastic deformation and annealing heat treatment on the microstructure and strength of the over-aged AA2024 has been investigated. 1, 3, 5 and 7 two-dimensional multi-directional forging passes carried out to the over-aged samples at room temperature as one of the methods of severe plastic deformation process. After applying strain, samples were subjected to annealing heat treatment at 200, 300 and 400 °C for 30 minutes and then quenched in water. For microstructural investigation, optical microscope and field emission scanning electron microscope images were prepared from the cut cross section of the samples and to evaluation the mechanical properties, the samples were subjected to hardness and compression test. Results indicate that with increasing the number of process passes, the grain is refined and consequently increasing mechanical properties including hardness and flow stress has occurred. Annealing heat treatment causes the occurrence of static recovery, grain growth, extended recovery and recrystallization phenomena, which is accompanied by a decrease in hardness and flow stress. Also, annealing at 400°C, in addition to the occurrence of recrystallization, is associated with the precipitation phenomenon. The precipitation caused by the instability and supersaturation of the network is due to the dissolution of metastable precipitates by applying severe plastic deformation and partial dissolution of the Sˊ/ S phase at this temperature. This issue causes the reduction of hardness and flow stress at 400 °C to be less than 300 °C
  9. Keywords:
  10. Aluminum Alloy 2024 ; Multidirectional Forging ; Annealing Heat Treatment ; Microstructure ; Mechanical Properties ; Severe Plastic Deformation ; Over Age

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