Loading...

The Effects of Y and ECAP on the Microstructure, Mechanical Behavior and Biodegradation of a Zn–1Mg Based Alloy

Aghajani Shirvani, Sina | 2025

0 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58549 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Alizadeh, Reza; Ashuri, Hossein
  7. Abstract:
  8. In recent years, zinc has attracted considerable attention as a base metal for temporary biomedical implants due to its biocompatibility and appropriate corrosion rate, although its poor mechanical properties have limited its applications. Alloying and applying severe plastic deformation are among the most effective approaches to improve these properties. In this study, the effects of adding 0.2 wt.% yttrium to the Zn–1Mg alloy and performing equal channel angular pressing (ECAP) on the microstructure, mechanical properties, creep behavior, stress corrosion cracking, and corrosion performance were investigated. The results revealed that the Zn–1Mg alloy exhibited a dendritic α-Zn structure with a eutectic Mg2Zn11 phase, while the addition of yttrium led to the formation of YZn₁₂ precipitates. The ECAP process resulted in grain refinement and a more homogeneous distribution of precipitates, yielding average grain sizes of 2.15 ± 0.07 µm and 1.69 ± 0.05 µm for the Zn–1Mg and Zn–1Mg–0.2Y alloys, respectively. Texture analysis indicated that ECAP introduced a strong crystallographic texture along the shear plane in both alloys. Mechanical testing showed that the ultimate shear strength (USS) of the Zn–1Mg alloy in the as-cast and ECAPed conditions was 141.6 ± 5.6 MPa and 197.5 ± 8.7 MPa, respectively, while for the Zn–1Mg–0.2Y alloy, these values were 159.7 ± 6.4 MPa and 217.6 ± 9.6 MPa, respectively. Creep testing demonstrated that the stress exponent of the yttrium-containing alloy was 6.8 in the as-cast state and 7.2 after ECAP, and the ECAP process reduced the creep rate at shear stresses of 120 and 130 MPa. In the stress corrosion cracking (SCC) tests, the corrosive environment did not cause a significant reduction in USS. For the as-cast Zn–1Mg–0.2Y alloy, the USS values in air and in the corrosive environment were 135.8 MPa and 130.9 MPa, respectively, whereas after ECAP, they were 51.2 MPa and 49.5 MPa, respectively. The addition of yttrium increased the corrosion rate in PBS solution; however, ECAP processing decreased it. Immersion tests showed that the corrosion rates of the Zn–1Mg alloy in the as-cast and ECAPed states were 0.204 mm/y and 0.114 mm/y, respectively, and for the Zn–1Mg–0.2Y alloy, 0.235 mm/y and 0.135 mm/y, respectively. Overall, the addition of yttrium combined with the ECAP process led to improved microstructure, higher strength, enhanced creep resistance in the Zn–1Mg–0.2Y alloy, and a reduction in the corrosion rate
  9. Keywords:
  10. Biodegradable Magnesium Alloys ; Severe Plastic Deformation ; Creep ; Zinc-Magnesium Alloys ; Equal Channel Angular Pressing (ECAP) ; Magnesium-Zinc-Yttrium Alloys

 Digital Object List

 Bookmark

No TOC