Date of Award

December 2020

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Engineering

First Advisor

Hugo Lopex

Committee Members

Benjamin Church, Wilkistar Otieno, Habib Tabatabai, Xiaoli Ma

Keywords

Biomedical, Casting of Reactive Metals, Implants, Light Weight Alloy, Magnesium Alloys, Novel Biodegradable Alloy

Abstract

Magnesium has been studied extensively due to the promising potential of using magnesium alloys in different applications, especially for biomedical implantation devices and other medical applications. This growing interest is due to the abundance of magnesium metal in the Earth's crust, as well as the fact that magnesium is 37% less dense than aluminum, has good mechanical properties, and is a nontoxic element with good biocompatibility. However, most Mg-based alloys contain alloying elements that are added to improve the mechanical properties but have toxic characteristics. At the same time a number of these alloys are still used in medical applications.

This proposed work focuses on designing and investigating a novel biomedical-biodegradable-nontoxic Mg-Mn-Zn-Na-K alloying system. Each of these alloying elements were selected based on two criteria. First, they fulfil the desired combination of biomedical-biodegradable-nontoxic alloying systems. Second, they improve the mechanical properties and corrosion behavior of relative to un-alloyed magnesium. Additionally, highly controlled melting and rapid cooling systems were developed for this study to reduce the processing defects and attain alloys with optimum properties. Furthermore, this work includes studying the effect of various cooling rates on the performance of pure magnesium made by casting in addition to investigating the effect of alloying elements. The fabrication of the alloys will be followed by four main characterization methods to determine the mechanical properties, corrosion performance, microstructure, and composition of the alloying systems.

The current study intends to develop a roadmap to analyze the effective factors in improving the performance of Mg alloys, starting from the selection of alloying elements and followed by the casting and solidification procedures. While the focus is on biomedical applications, developing casting and alloying systems for Mg alloys could be applied to other applications such as the automotive and aerospace industries due to the light weight and abundance of Mg.

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