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Investigating the Microstructure, Mechanical Properties and Biodegradation Behaviour of Mg‒1Zn‒0.2Ag/MgO Composites

Hashemi, Mohammad | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 57825 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Alizadeh, Reza; Aashouri, Hossein
  7. Abstract:
  8. Magnesium and its alloys have gained a lot of interest recently in the field of biodegradable implants, particularly in the field of orthopedics, mainly due to their excellent compatibility, low density and similarity of their mechanical properties with the human bone. However, the main weakness of magnesium for such applications is that it corrodes faster than the time required for complete healing of the tissue. Different properties of Mg can be improved by making composites. In this research, 1% and 2% of MgO microparticles were added to the Mg-1Zn-0.2Ag alloy. These composites were made by the stir casting technique, and after that, the samples' microstructure, mechanical characteristics, and biodegradability were examined. It was found that adding 1% of MgO particles produced an almost uniform distribution, while only a small number of particles were agglomerated. In contrast, adding 2% of MgO particles produced a composite with a less uniform distribution and more agglomerated areas. Mechanical tests revealed that the increase of MgO particles increased both the shear strength and Vickers hardness of the alloy. For these composites, two strengthening mechanisms were identified: load transfer as the primary mechanism and grain boundary strengthening as a secondary mechanism. Nevertheless, a different trend was observed in degradation tests. The electrochemical and immersion tests results indicated that the sample with 1% MgO reinforcement exhibited a lower corrosion rate than the sample with 2% MgO reinforcement, and the corrosion resistance of the alloy was weaker than both composites. It was concluded that the MgO particles resulted in the formation of a denser protective film of Mg(OH)2. Furthermore, the Mg-1Zn-0.2Ag/MgO composites often exhibited superior corrosion behavior compared to the Mg-1Zn-0.2Ag alloy
  9. Keywords:
  10. Magnesium Alloy ; Biodegradable Magnesium Alloys ; Mechanical Properties ; Reinforcement Distribution ; Magnesium Oxide Particles ; Corrosion Behavior

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