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Prediction of Microstructure Evolution of Severely Deformed Pure Aluminum during Annealing

Jafari, Rahim | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41432 (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) Processes have drawn lots of attention due to their ability to refine grain size and develop some properties of bulk metals and alloys. After deformation, however, ductility and formability of metals are reduced. Annealing has been used as a solution for improvement of these characteristics after deformations even after SPD processes. On the other hand, there is a possibility that during annealing grains could grow, therefore it can neutralize the effect of SPD process. Consequently, predicting behavior and evolution of microstructure during annealing finds an important role. In this research, accordingly, vertex model have been used in order to predict evolution of severely deformed aluminum during annealing in 250 and 350 oC. Also, a new algorithm base on voronoi tessellation in laguerre geometry has been proposed to simulate this microstructure for the first time. To verify the simulated microstructure, constrained groove pressing (CGP) has been used as a SPD process. Different strains were imposed on aluminum sheets by CGP process. Then samples annealed in the mentioned temperatures. Microstructures of these samples, before and after annealing, were analyzed by means of scanning electron microscope (SEM) and electron back scatter diffraction (EBSD). Growth parameters are calculated from simulations’ results. In 250 oC, calculated growth power is close to one which shows a normal grain growth. This result is in a good match with data obtian by experimental analyses. Though in 350 oC both experimental and simulation depicts abnormal grain growth. Micrographs of annealed sample in this temperature depicts that grain growth ratio was high and recrystallization starts at the very beginning. Growth exponent here is about 1.5 to 2 for samples with different imposed strains
  9. Keywords:
  10. Forecasting ; Aluminum ; Severe Plastic Deformation ; Voronoi Diagram ; Annealing ; Vertex Model

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