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Theoretical and Practical Study of Softening Kinetics after Deformation at Elevated Temperature in an Aluminium Alloy

Mirdar Harijani, Mehdi | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51508 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Serajzadeh, Siamak
  7. Abstract:
  8. In this study, behavior of softening after hot tensile and hot rolling processes in isothermal and non-isothermal conditions in AA5083 Aluminium alloy has been simulated using cellular automata. Also effect of temperature and strain rate in hot tensile test and effect of temperature and strain in hot rolling has been investigated. First distribution of temperature in material using the finite element method computed and used as initial temperature in CA and computing the static recovery in hot tensile. Also for hot rolling, computing static recovery and CA are used for initial temperature in ABAQUS. For investigating effect of dynamic recovery and recrystallization, the neural network has been used as entry in CA method. For computing effective strain in different layer of sample which rolled, ABAQUS has been used. For computing the initial microstructure, spatial saturation nucleatin and also topology changing from deformation is computed for initial microstructure. In recrystallization microstructure simulation, continuous nucleation has been used and nucleation rate, velocity of grain boundary migration and curvature of grain boundary to be considered. To validation the simulation results, experimental tests achieved. Samples at the temperature of 180, 220, 260, 300, 340 and 380 ̊C in strain rates of 0.002, 0.005, 0.01, 0.026, 0.03 and 0.05(1/S) for one hit and two hit condition are tensiled at high temperature and for nomination the microstructure in isothermal and non-isothermal conditions after tensile test are tempered. Initial strain in these samples are 20%. Hot rolling at the temperatures of 350, 400 and 460 ̊C in the rolling velocity of 50rpm for the samples with diameter of 4mm with the strain of 0.25 and 0.4 has been done. Results of hot tensile test shows that for isothermal condition at 340 ̊C, despite of softening with deformation at high temperature, the static recrystallization is lot and at 380 ̊C during deformation, because of dynamic softening, a lot of new nuclie are nucleated and will growth and causes decreasing of the internal energy in the material. In non-isothermal condition, because of decreasing the temperature of sample, the rate of nucleation and growth is lower. In high temperature rolling samples, the size of grain at the surface and center of the sample has been compared which at the surface because of the slip spirant stress and additional working, more equation strain applied and the energy for nucleation is more and the grains are finer
  9. Keywords:
  10. Hot Rolling ; Static Recovery ; Static Recrystallization ; Finite Element Method ; Neural Network ; Cellular Automata ; Hot Tension ; Aluminum Alloy 5083 ; Softening

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