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Effect of Temperature and Strain Rate on the Nano-Structure Produced by ASB Process in Production of Aluminum CNG Cylinders

Alinaghian, Hossein | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42709 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Akbarzadeh Changiz, Abbas
  7. Abstract:
  8. Accumulative spin bonding as a severe plastic deformation process results in a finer microstructure through multi-pass processing. This method consists of successive and repeated preparation of internal and external surfaces of two similar tubes, simultaneous flow forming of two tubes and production of a tube with the same thickness as the primary one. This word was conducted to study the effect of different rotational speeds and different cooling environments on the mechanical properties and microstructure of AA1050 tubes. The samples were prepared with 0.8 mm thickness and 92.8 mm internal diameter through four passes of ASB with 250, 500, 710 rpm under air, water and acetone cooling conditions. Variation of the mechanical properties was investigated by tensile tests and microhardness measurements. Also, the microstructure was determined by Differential Scanning Calorimetry and X-ray diffraction as well as optical microscopy. The results indicate that the hardness and strength are decreased with increasing deformation due to low adiabatic heating. XRD results show that the residual stresses are strongly dependent on temperature. In fact, residual stresses and the strength are increased by temperature decline due to increase of the dislocation density. Increase of the dislocation density with decreasing temperature is also evident by the DSC test results. It is shown that by increasing the number of passes, finer final grain sizes lead to higher strengths and hardnesses
  9. Keywords:
  10. Accumulative Spin Bonding (ASB)Process ; Ultra Fine Grain Structure ; Severe Plastic Deformation ; Zener-Holomon Parameter

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