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Theoretical and Practical Study of Deformation Behavior of AlMg6 Alloy

Gholamzadeh, Abolfazl | 2011

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 42414 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Karimi Taheri, Ali
  7. Abstract:
  8. Aluminum alloys are widely used in many applications in aerospace and automotive industries. Therefore, the study of the effects of different parameters such as chemical composition, temperature, strain, strain rate and recovery and recrystallization phenomena being more effective on controlling of microstructure and final properties of product, are more important. In this research, deformation behavior of AlMg6 alloy has been studied from two theoretical and experimental views as described below: In ambient temperature deformation, the mechanical properties in correlation on the microstructures developed at different temperatures have been assessed. The results of tensile test demonstrated that the occurrence of dynamic strain ageing is due to the hardening effect of solved atom that diffused into dislocation. In ambient temperature of ECAE process, the effects of strain paths and different passes of ECA deformation is investigated on the hardness distribution and microstructure of the alloy and also, thermal stability of ECAEed and rolled samples are competed. It is concluded that the structural stability of rolled samples is higher than ECAEed samples. Constitutive equations for the former and ECAEed samples are extracted from flow stress curves and hot deformation behavior of alloy is modeled. The average value of activation energy was derived as 132 KJ/mol and 169.21 KJ/mol for the former and ECAEed samples respectively. The results showed the occurrence of dynamic recrystallization phenomena at high temperatures or low strain rates. To analyze of deformation behavior of alloy, a finite element code, ABAQUS, is employed to solve the governing equations of heat conduction and plastic deformation and the strain and stress distribution is modeled. Also, optimum range of deformation zone (strain rate and temperature) has been demonstrated by training corrected data of hot compression test of neural network. Two stage hot compression test showed that static softening, at constant strain rate, does not noticeably occur with increase of delay time between the deformation stages, whereas, softening rate highly enhanced with decrease of strain rate at constant delay time. The increasing of the m values from 0.1 to 0.4 for the applied strain rate ratios of (10/100) and (1:10), respectively, is assumed to be the result of changing the deformation mechanism from recovery to recrystallization
  9. Keywords:
  10. Metals Forming ; Dynamic Recrystallization ; Hot Deformation ; Hot Compression ; Equal Channel Angular Extrusion (ECAE)

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