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Investigation of the Effect of Lithium Addition on the Microstructure, Mechanical Properties, and Biodegradability of Zn-Mg Alloys

Malekian, Zahra | 2025

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58522 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Alizadeh, Reza; Ashouri, Hossein
  7. Abstract:
  8. Nowadays, zinc has attracted significant attention as a biodegradable material due to its suitable degradation rate and the absence of harmful gas evolution during degradation. However, the relatively poor mechanical properties of zinc necessitate improvement through alloying. In this regard, the present study investigates the effect of lithium addition on Zn-Mg alloys. The addition of lithium to Zn-Mg alloys remarkably enhances their mechanical and corrosion properties. The main objective of this study is to improve the mechanical properties while maintaining the corrosion resistance of Zn-0.5Mg and Zn-1Mg alloys by adding various amounts of lithium, aiming to meet the functional requirements of biodegradable implant applications. The microstructure of Zn-Mg-Li alloys consists of primary zinc dendrites and a eutectic structure containing Zn along with intermetallic phases LiZn₄ and Mg₂Zn₁₁. The results of mechanical testing showed that lithium addition significantly improved the mechanical properties of the alloys. The maximum shear strength of the Zn-0.5Mg-0.15Li alloy increased to about 250 MPa, compared to approximately 150 MPa for the base Zn-0.5Mg alloy, indicating a notable enhancement. Moreover, the macrohardness of this alloy increased from 60 Vickers to 100 Vickers. Microhardness measurements also revealed increased hardness in both the eutectic structure and the α-Zn matrix in the presence of lithium. A similar trend was observed in the Zn-1Mg-0.3Li alloy, where the maximum shear strength reached 270 MPa and the hardness increased to 130 Vickers. Corrosion behavior, evaluated by immersion testing in PBS solution, showed that lithium-containing samples exhibited lower corrosion rates after 28 days compared to the base alloys. Electrochemical tests also indicated a shift in corrosion potential toward more negative values accompanied by a reduction in corrosion rate, attributed to the formation of stable protective layers on the surface of the lithium-containing alloys. These layers effectively controlled and slowed the further progress of corrosion. In conclusion, the addition of lithium to Zn-Mg alloys significantly enhances both mechanical properties and corrosion resistance, making these alloys promising candidates for use in biodegradable implants with improved performance and higher safety
  9. Keywords:
  10. Mechanical Properties ; Corrosion Resistance ; Corrosion Properties ; Zinc-Magnesium Alloys ; Biodegradable Implants ; Biocompatibility

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