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Effect of Strain Path on Static Recrystallization Behavior of a Steel

Afshari, Elham | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40375 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Serajzadeh, Siamak
  7. Abstract:
  8. Static recrystllization in low carbon steel after two type of deformation –sidepress as an inhomogeneous deformation and rolling as a common industrial process - has been simulated using Cellular Automata (CA). The finite element method was utilized to compute the strain and stored energy distribution due to deformation. The initial microstructures were created by simulation of recrystallization with homogeneous site-saturated nucleation and topologic deformation was also considered in model. Subsequently using the result of FEM, stored energy of deformation was calculated and transferred into a two dimensional CA lattice. Nucleation rate and grain boundary velocity were considered inhomogeneous as a function of stored energy. Experimental studies were also performed In order to verify the result of simulation. Rolling process and sidepress test were performed in different amount of reduction. Then the specimens were annealed isothermally at 600ºC and 700ºC and some specimens were taken out of the furnace at increasing interval times and their hardness values were measured to determine recrystallized fraction. Then the metallographic examination was performed on the cross section of specimens. The results of simulation show that the inhomogeneous distribution of nuclei, leads to low values of the JMAK slope and also decreases of the JMAK slope by proceeding recrystallization. The Avrami exponent achieved for sidepressed specimen from simulation was 2.5 and from experimental result was 2.2-2.6 also for rolling it achieved 2.6 for simulation and 2-2.6 for experimental result. Kinetic of recrystallization decrease as a result of hydrostatic pressure but it doesn’t have effect on Avrami exponent and recrystallized grain size. By comparing the modeling results and the experimental data, it is concluded that the presented model successfully predict the kinetic and recrystallized microstructure, Therefore, it can be used to predict the recrystallized grain Size distribution and recrystallization kinetic.

  9. Keywords:
  10. Static Recrystallization ; Low Carbon Steel ; Finite Element Method ; Microstructure Simulation ; Cellular Automata ; Recrystallization kinetics

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