Surveying The Biodegradation Behavior, Biocompatibility and Mechanical Properties of Mg-4Zn-xAl-0.2Ca Alloys

Homayun, Bahman | 2013

783 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 45187 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Afshar, Abdollah
  7. Abstract:
  8. Due to their favorable biodegradability, Magnesium and its alloys have always attracted such a lot of research interests for making temporary implants. With the same direction, Mg-4Zn-0.2Ca has recently absorbed lots of research interests, due to its excellent biocompatibility. As the most regarded draw back concerned with this alloy, poor corrosion resistance is frequently discussed. Accordingly, in the present work it has been tried to come over this problem by addition different amount of aluminum, including 1, 3, 5, 7.5, and 10 percent, to this alloy; without causing any negative effect on its biocompatibility, and to present a new alloy composition with modified degradation behavior.
    Results showed that addition of Al up to 3% can prevent the formation of secondary phases. As a results, corrosion current densities were reduced from 148 µA.cm^(-2) in Mg-4Zn-0.2Ca to 112 µA.cm^(-2) in Mg-4Zn-1Al-0.2Ca, and 84 µA.cm^(-2) in Mg-4Zn-3Al-0.2Ca. With the same direction, Corrosion rates determined by the immersion tests were 2.26 mmy, 1.1mmy, and 0.65 mmy for the alloys respectively. On another point of view, formation of considerable amounts of boundaryand phases, alloys containing 5, 7.5, and 10 percent alloys exhibited extraordinary high corrosion current densities,1200 µA.cm^(-2),1440 µA.cm^(-2),and 1500 µA.cm^(-2)respectively.
    All in all, Mg-4Zn-3Al-0.2Ca with a degradation rate about 4 times lower and an ultimate tensile strength about 20% better than former alloy composition was presented as a better alloy composition respected to the former one. Considerable decrease in the formation of the boundaryand phases, including MgZn, Ca2Mg6Zn3, Al5Mg11Zn4 and Al_12 Mg_17 developing several micro galvanic corrosion systems, is the most regarding parameter responsible for this modification in the alloys degradation behavior
  9. Keywords:
  10. Biocompatibility ; Biodegradability ; Mechanical Alloying ; Magnesium-Aluminum-Zinc Alloy ; Magnesium Alloy

 Digital Object List