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The Effect of Non-isothermal Annealing on the Microstructure and Mechanical Properties of Severely Deformed Aluminum 1xxx

Khodabakhshi, Amir Reza | 2017

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 50040 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Kazeminezhad, Mohsen
  7. Abstract:
  8. Multi-directional forging is used as a severe plastic deformation process for producing ultrafine grained materials in which a sample undergoes consecutive compressive strains and as a result, coarse grains break to smaller grains. The strength of multi-directionally forged material increases because of grain refinement, although the high strain energy reserved in a sample after large plastic deformation lessens its ductility. Metals experience non-isothermal heating cycle during annealing till they reach the target temperature. Non-isothermal heating cycle can affect microstructure and mechanical properties of severely deformed material due to its high strain energy. Thus, investigation of non-isothermal annealing of severe plastically deformed materials is of great importance. In this work, 1000 series aluminum samples underwent strains of 1, 2 & 3 by applying 2, 4 & 6 passes of multi-directional forging and then were annealed non-isothermally up to 150, 200, 250, 300 & 350 °C. Evolution of dislocations density and flow stress was studied via modeling for deformation and annealing stages. It was found that 2, 4 & 6 passes multi-directionally forged samples show thermal stability up to temperatures of 250, 250 & 300 °C respectively. Theoretical and experimental results were compared and reasonable agreement was observed in severe plastic deformation and non-isothermal annealing modeling. A proposed non-isothermal annealing model is based on an intragranular dislocations density evolution and as a result, 2 & 4 passes multi-directionally forged samples annealed non-isothermally up to 350 °C and showing grain growth in addition to reduction of dislocations density, have a lower experimental flow stress in comparison with the predicted flow stress
  9. Keywords:
  10. Thermal Stability ; Microstructure ; Severe Plastic Deformation ; Aluminum ; Aluminum Alloy Series 1xxx ; Nonisothermal Anealing

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