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Modeling the Mechanical Properties of Aluminum Series 1xxx after Severe Plastic Deformation in Corrugation Die

Hosseini, Ehsan | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 39530 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Kazeminezhad, Mohsen
  7. Abstract:
  8. Nowadays, modeling the behavior of materials during forming processes is so important. The role of most of them is to investigate and predict the evolutions of microstructure and mechanical properties of materials during plastic deformation. Previous researches have demonstrated that the best parameter to investigate these evolutions is the dislocation density of materials. In this study, first, the dislocation-based models, which investigate the material parameters evolutions during plastic deformation, were investigated and it was revealed that among all presented models, only the two internal variables models can investigate the behavior of materials during severe plastic deformation. The model, by considering the evolutions of cell interiors and cell walls dislocation densities, predicts the evolution of microstructure and mechanical properties of material during deformation. In following, the validity of model was examined by imposing the model to different materials and processes. As consequence, the problems, deficiencies and modifications of the model were extracted and reported through published papers. At last, it is concluded that the investigation of materials behavior by considering just two internal variables of cell interiors and cell walls dislocation densities is not possible. Therefore, a new model was proposed that is based on physical assumptions and by considering both edge and screw dislocations in three categories of mobile dislocations, immobile cell interiors dislocations and immobile cell walls dislocations can investigate the behavior of materials during deformation. To examine the validity of proposed model, the process of constrained groove pressing of aluminum sheets was chosen. The process, which has been recently presented as a severe plastic deformation process on metallic sheets, includes repetitive deformation of sheets by grooved and flat dies. In the present study for the first time, the strain magnitude of about seven was imposed to the materials through this process and the produced materials were examined using the transition electron microscopy, X-ray diffraction, tensile and hardness tests. Comparing between the modeling and experimental results shows a good agreement between them. Also, it is interesting to note that the proposed model can be counted as unique model witch can predict all six stages of work hardening, Although, these six stages were reported by previous experimental researches.
  9. Keywords:
  10. Severe Plastic Deformation ; Dislocation Density ; Modeling ; Mechanical Properties ; Cell Size ; Flow Stress

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