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Processing Thin Magnesium Tubes by TCAP Process with Trapezoidal Geometry and Fabrication of Magnesium Microtubes with a Novel Method

Kamran Masouleh, Mohsen | 2022

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 55179 (08)
  4. University: Sharif University of Technolog
  5. Department: Mechanical Engineering
  6. Advisor(s): Assempour, Ahmad
  7. Abstract:
  8. Due to compability of Magnesium with the body, it is a suitable material for making biodegradable stents, Althogh, its mechanical properties are not desirable for stent application. Accordingly, lately, magnesium’s microstructure and mechanical properties have been improved using various methods, including the process of severe plastic deformation (SPD). Many severe plastic deformation methods have been introduced for the fabrication of ultrafine grain tubes till now, which the process of tubular channel angular pressing (TCAP) is the most effective one. In the first part of the research, Magnesium tubes with a thickness of 1 mm were processed using the TCAP with a trapezoidal channel, and then the effect of pass number and temperature on the microstructure and mechanical properties of the processed tubes were investigated. Based on the tensile test results, the elongation value in all samples during one-pass process has increased. The highest increase in yield strength and ultimate strength occurred at 250°C in one-pass sample, which are 1.43 and 1.32 times higher than the initial sample, respectively. The average minimum grain size is 3 µm, which is calculated in 3 passes sample at 200°C. Since the sample’s dimensions do not change in SPD processes, it is necessary to use the extrusion process after applying the SPD process in order to produce microtubes. Therefore, in the second part of this study, a magnesium microtube with a thickness of 0.5 mm is made by combining the SPD process and the extrusion process. Magnesium microtubes are fabricated at two temperatures of 300 and 350°C. The results show that the improvement of mechanical properties of microtubes made at 350°C is more significant than others. The yield strength, ultimate tensile strength, and elongation have increased 1.32, 1.73 and 1.34 times higher than the initial sample, respectively.
  9. Keywords:
  10. Severe Plastic Deformation ; Magnesium ; Tubular Channel Angular Pressing (TCAP) ; Combination Process ; Microtube ; Yield Strength

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