Investigation of Magnesium-Lithium-Zinc-Calcium Alloys for Biomedical Applications

Authors

Chiamaka Okafor, Florida International UniversityFollow

Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Materials Science and Engineering

First Advisor's Name

Norman Munroe

First Advisor's Committee Title

Committee chair

Second Advisor's Name

Arvind Agarwal

Second Advisor's Committee Title

Committee member

Third Advisor's Name

Darryl Dickerson

Third Advisor's Committee Title

Committee member

Fourth Advisor's Name

Sharan Ramaswamy

Fourth Advisor's Committee Title

Committee member

Fifth Advisor's Name

Puneet Gill

Fifth Advisor's Committee Title

Committee member

Keywords

Magnesium alloys, magnesium-lithium alloys, bioresorbable alloys, biodegradation, corrosion, mechanical properties, nanoindentation, thermomechanical processing, XPS, EIS, Eutectic solidification

Date of Defense

10-31-2022

Abstract

Alloy design is a fundamental approach to developing Mg-based bioresorbable implant materials that possess the desired mechanical and degradation behavior required for treatment. Mg-Zn-Ca alloys have received significant interest as bioresorbable implant materials because of superior mechanical properties and lower degradation rates. However, they are prone to localized corrosion, which jeopardizes their mechanical strength and causes premature implant failure. In this study, lithium has been added to Mg-1Zn-0.5Ca to promote uniform degradation and room temperature ductility. Alloys with Li content up to 4 wt.% exhibited a hcp structure, with ~12% elongation and evidence of pitting. Alloys with 8 wt.% Li had a duplex structure, with ~30% elongation and no evidence of pitting. Alloys with 11 wt. % exhibited a single-phase bcc structure, with ~33% elongation and a lithium carbonate surface coating. The 8 and 11 wt.% Li alloys had a reduced metal dissolution, which resulted in a high viability of HUVEC cells, making them attractive for biodegradable stent materials. These simultaneous improvements in mechanical and degradation properties of these Mg-Li-Zn-Ca alloys were achieved through a reduction in precipitation of secondary phases, formation of a lithium carbonate surface coating and phase transformation from a hexagonal close packed to a duplex and body centered cubic structures. In addition, higher hardness, and elastic modulus achieved for these alloys are desirable to prevent stent recoil after deployment. Rolling, which is an important metal forming process in the manufacturing of metals and alloys, has been adopted as a thermomechanical process for these designed alloys. The effects of both cold and hot rolling on the alloys uncover their response to plastic deformation and demonstrates their formability and manufacturability.

Identifier

FIDC010833

ORCID

0000-0003-2669-7005

Recommended Citation

Okafor, Chiamaka, "Investigation of Magnesium-Lithium-Zinc-Calcium Alloys for Biomedical Applications" (2022). FIU Electronic Theses and Dissertations. 5190.
https://digitalcommons.fiu.edu/etd/5190