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Investigating the Effect of Heat Treatment and Incorporation of Y on the Microstructure, Mechanical Properties and Corrosion Behavior of Biodegradable Mg-3Sn Alloys

Jalali, Melika | 2025

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58215 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Alizadeh, Reza; Ashuri, Hossein
  7. Abstract:
  8. Magnesium metal has attracted attention as a base material for the fabrication of temporary implants due to its biocompatibility and mechanical properties similar to human bone. However, its rapid degradation and mechanical integrity loss in physiological environments have limited its applications. To enhance the overall properties of magnesium-based implants, alloying and heat treatment are considered effective metallurgical approaches. To enhance the characteristics of Mg-3Sn, 1% yttrium (by weight) was added, followed by solution heat treatment and ageing heat treatment. The microstructure analyses revealed that in the as-cast state of both alloys, the matrix consists of the alpha-magnesium phase along with multiple precipitates. For the Mg-3Sn alloy, the only intermetallic phase observed was Mg2Sn, while the addition of yttrium led to the formation of MgSnY and Sn3Y5 precipitates alongside Mg2Sn. Solutionizing treatment resulted in the complete dissolution of precipitates in the Mg-3Sn alloy, while in the Mg-3Sn-1Y alloy, it dissolved Mg2Sn precipitates and improved the distribution of other precipitates. Additionally, precipitation hardening produced nanosized Mg2Sn particles in both samples. The mechanical properties, including strength and hardness, were evaluated. The results showed that the ultimate strength and hardness of the Mg-3Sn alloy in as-cast, solutionized, and precipitation-hardened states were approximately 106 MPa, 113 MPa, and 122 MPa, and 26 HV, 30 HV, and 35 HV, respectively. For the Mg-3Sn-1Y alloy, these values were 117 MPa, 120 MPa, and 129 MPa, and 39 HV, 41 HV, and 45 HV, respectively. The improvements in hardness and strength with the addition of yttrium and heat treatment were attributed to the formation of precipitates and solid-solution strengthening. Corrosion behavior was investigated The results indicated that adding yttrium reduced the corrosion rate in all conditions compared to the Mg-3Sn alloy. The highest corrosion rate was observed in the as-cast Mg-3Sn alloy, measuring 27.16 mm/year, while the lowest corrosion rate was obtained for the solutionized Mg-3Sn-1Y alloy at 4.19 mm/year
  9. Keywords:
  10. Mechanical Properties ; Corrosion Resistance ; Heat Treatment ; Biodegradable Magnesium Alloys ; Biocompatibility ; Magnesium-Tin Alloy ; Biomedical Implants ; Biodegradable Implants

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