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An Investigation on the Microstructure and Mechanical Properties of Almg6 Alloy-Carbon Nanotube Composite Produced by Accumulated Roll Bonding Process

Sasani Sarvestani, Farnaz | 2017

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 50231 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Karimi Taheri, Ali
  7. Abstract:
  8. In recent years, the use of high specific strength aluminum alloys in automotive and aerospace industries is in progress due to their energy savings. On the other hand, the carbon nanotubes (CNTs), due to their ultra-high strength and modulus of elasticity, have been considered as an excellent reinforcement for the metal matrix composites used in these industries. For production of these materials, the severe plastic deformation (SPD) has been known as a method of grain refinement to increase the strength and ductility. In this research, the composites of AlMg6 reinforced with CNT were produced by accumulated roll bonding (ARB) known as a SPD technique and their properties were compared with those of AlMg6 alloy ARBed at the same conditions as the composites. The CNTs were used in two different conditions consisted of ball milled with aluminum powder and without any treatment. To assess the effect of partial annealing on mechanical properties, AlMg6/CNT-Al and ARBed-AlMg6 at temperatures of 200, 260, 300, 350 and 400 ° C were heat treated. Also, metallography examination, tensile and hardness tests were carried out to evaluate the optimum conditions of the process parameters such as the number of rolling pass, ARB temperature, the amount of CNT, on the microstucture, tensile properties, and formability of the composites. The results indicated that an AlMg6-CNT composite of mean grain size of 500 nanometers together with a tensile strength being 20% higher than that of AlMg6 alloy ARB-ed without any CNT can be produced. Moreover, the AlMg6/CNT-Al composite exhibit a higher formability compared to ARBed-AlMg6 material. Using the JMAK theory in conjunction with the hardness data and aneealing treatment results, the activation energy for static recrystallization of the AlMg6/CNT-Al composite and ARBed-AlMg6 material was determined as 94 and 148 kJ. Mol-1, respectively, indicates that the CNTs and ARB have enhanced the kinetics of recrystallization of AlMg6 alloy
  9. Keywords:
  10. Accumulative Roll Bonding (ARB) ; Forming Limit Diagram (FLD) ; Mechanical Properties ; Milling ; Annealing ; Roll Bonding ; Aluminum-Magnesium Reinforced Carbon Nanotube Alloy (ALMg6/CNT) ; Annealing

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