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Modeling the Effect of Stacking Fault Energy on Severe Plastic Deformation of Metals

Parvin, Hooman | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 46904 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Kazeminezhad, Mohsen
  7. Abstract:
  8. Nowadays, modeling the deformation behavior of materials is an indispensable tool to describe the evolutions of microstructure and mechanical properties of materials during deformation. As previous investigations have shown, the dislocation density is the most appropriate parameter for investigating the deformation behaviour of materials. In present research, considering the effect of stacking fault energy (SFE), the deformation behavior is investigated. In this regard, at first a thermodynamics based modeling of deformation is presented. Previous studies have shown that due to heterogeneous distribution of dislocations during severe plastic deformation, it is needed to use multi-variable models instead of one-variable ones. In this regard a two-variable dislocation density model is presented which considers the effect of stacking fault energy and predicts the evolutions of microstructure parameters and mechanical properties such as dislocation density, cell size and strength. The calculations show that the total dislocation density, dislocation density in cell interiors, dislocation density in cell walls and flow stress are decreased with increasing SFE. To verify the model results, they are compared with the experimental data and a good agreement is observed. In addition, the modeling predictions are compared with results of previous theoretical studies of severe plastic deformation. Moreover, in another section, a two-variable dislocation density based model, ETMB (Estrin, Toth, Molinari, Brechet), is investigated. Previous formulation of ETMB is based on the empirical and mathematical expressions and does not consider the effect of stacking fault energy. The model is developed to a physical-metallurgical based model, which considers intrinsic parameters such as stacking fault energy. Moreover, the developed model considers different mechanisms for the annihilation of the dislocations in the subgrain interiors and subgrain boundaries. In addition, in the last chapter, the effect of stacking fault energy on the equilibrium grain size during severe plastic deformation is investigated. The modeling results are compared with the reported experimental data and a good agreement is obtained
  9. Keywords:
  10. Modeling ; Stacking Fault Energy ; Severe Plastic Deformation ; Dislocation Density

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