Himesha Abenayake

Biodegradable Zn alloys show high potential for use in various biomedical applications, including stents, orthopaedic screws and fracture fixation plates. This potential stems from their ability to degrade within a physiological fluid, which thereby eliminates the need for secondary revision surgeries when used as an implant material. In fact, of the three main biodegradable metals (i.e., Fe, Mg, and Zn), Zn shows the most optimal degradation rate suitable for biomedical implants. In addition, Zn boasts good biocompatibility, is an essential nutrient for the human metabolism and plays a critical role in cellular neuronal systems. However, the major factor hindering the full-scale potential of Zn alloys for biomedical implants is their poor mechanical strength. Zn has a low static recrystallization temperature which can result in a significant loss of mechanical strength once implanted and exposed to human body temperature. In addition, Zn displays natural age hardening at room temperature which results in a potential deterioration of mechanical strength during storage prior to implantation. Moreover, Zn has demonstrated strain-rate sensitivity, whereby its strength and ductility are strongly impacted by the rate at which the material is deformed.

Recent studies demonstrate an interdependence on both alloy chemistry and processing when seeking to alleviate such issues. However, such studies have been mostly limited to conventional processing (e.g., casting, extrusion) and solely binary Zn alloys. In this regard, this doctoral thesis will aim to address the aforementioned issues associated with mechanical properties of Zn, primarily seeking to design a multi-component (> 2 elements) biodegradable Zn alloy suitable for processing by powder bed fusion-laser beam. The goal is to design unique microstructures, with improved stability (i.e., resistance to static recrystallization, strain-rate sensitivity, and room temperature aging), enabling high strength and excellent degradative properties, suitable for next-generation biodegradable metallic implants.