Abstract:

Magnesium and its alloys are promising biodegradable metal scaffolds for potential bone regeneration applications, such as bioabsorbable implants. However, for this to be possible, further developments are necessary. On the one hand, Mg tends to corrode at a high rate, leading to excessively high hydrogen release rates that can be toxic in cellular environments. Thus controlling the degradation rate is crucial. On the other hand, it is necessary to use novel processing techniques that allow the manufacturing of Mg scaffolds with the advanced irregular geometry, controlled porosity, and adequate mechanical properties necessary for this application.

One of the strategies that can limit the rate of corrosion is to add alloying elements to the Mg. The addition of rare earth elements (RE) could improve both mechanical strength and corrosion resistance. Among Mg-RE alloys, WE43 has been considered suitable for biomedical applications in preclinical trials. However, manufacturing of Mg scaffolds by conventional techniques is complicated, requiring complex and fully interconnected porous structures in combination with adequate stiffness and strength, resembling the structure of bone.

Recently it has been possible to 3D print Mg alloy scaffolds using selective laser melting (SLM) techniques, but it is necessary to determine their mechanical properties, biodegradation behavior, and their interconnection. Therefore, this thesis project aims to understand the microstructure-topology-mechanical properties relationships in a Mg alloy (WE43) with crosslinked structure, produced by additive manufacturing for biomedical applications.

Within the first year of this thesis, results concerning the degradation rate and mechanical properties using advanced characterization techniques are presented. In particular, strut size, as well as the micro-architecture of the scaffolds, seem to be controlling factors for the mechanical properties. The influence of post-treatments such as electropolishing and PEO coatings to obtain a good biological behavior is also remarkable.