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An Investigation into the Microstructure and Mechanical Properties of Biodegradable Magnesium Alloys Composite-carbon Nanotube Produced by the Mechanical Alloying and Powders Pressing Processes

Naseri, Maryam | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51037 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Karimi Taheri, Ali
  7. Abstract:
  8. Properties of biomaterials, especially in application as planting, can be controlled and optimized by alloying and hardening sedimentation. In recent years, the study on the simultaneous improvement of mechanical properties, toughness and corrosion behavior of magnesium composite by carbon nanotubes (CNTs) is very limited. In this study, the behavior of mechanical properties and corrosion of magnesium alloy composites with different percentages of CNTs have been investigated. The production of magnesium alloy composite by powder metallurgy and aging process have been used as effective methods for improving mechanical properties and increasing the corrosion resistance of magnesium alloys. For this purpose, an alloy powder and then a composite powder with different percentages of CNTs were produced by a mechanical mill during 8 hours. The results of this section showed that CNTs are well dispersed in the matrix, and by increasing the content of the CNTs, the powder has a hardened strain and a smaller particle size. In the second part, after pressing the produced powders, spark plasma sintering process was performed. The results showed that CNTs had a very significant effect on the sintering and mechanical properties of the composites. So that the density of material was 100% for 1% by weight of CNTs, and the shear strength of this composite (79.8 MPa) increased 46% compared to the alloy sample (54.6 MPa). In the next step, the effect of CNTs on solubility and aging were investigated. The solvent operation was carried out at 455 °C and the aging process was carried out at 125°, 175° and 200°C. The results showed that enhancement of CNTs up to 1% by weight increased the shear strength compared to the alloying sample, and in the aging stage, increasing the CNTs to 1% by weight, accelerated the aging process and increased the shear strength. The maximum shear strength was obtained at a temperature of 175 °C and an aging time of 40 minutes. Finally a polarization method was used to evaluate the corrosion behavior. The results showed that the CNTs improve the corrosion resistance of composites compared to magnesium alloys in the spark plasma stage. Also, in composite containing 1 wt% of CNTs, the effect of aging process was very effective and the corrosion resistance of this composite increased significantly
  9. Keywords:
  10. Mechanical Properties ; Carbon Nanotubes ; Shear Punch Test ; Polarization ; Powder Press ; Biodegradable Magnesium Alloys ; Magnesium-Carbon Nanotube Alloy Composite

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