Investigation of Hot-extrusion Effect on Microhardness, Microstructure and Corrosion Behavior of Magnesium-based Bio-composites

Magnesium alloys are a unique choicefor orthopedic implants due to their biocompatibility and biodegradability properties. In this article, the impact of hot-extrusion process is investigated on microhardness, microstructure, and corrosion behavior of magnesium/2.5wt% hydroxyapatite (HA) rods as a bio-composite. Hot extrusion process was implemented on the as-cast samples in two different steps resulting two various total extrusion ratios of 5:1 and 20:1. The corrosion susceptibility of the extruded composites was studied by polarization test in simulated body fluid (SBF) as a corrosive environment. According to the results, adding hydroxyapatite reinforcing particles and applying higher extrusion ratios caused grain refinement in the matrix comparing to the pure magnesium. Moreover, while the hardness of the pure magnesium sample decreased slightly after the second extrusion pass, it was enhanced in the composite specimens. Besides, both extrusion ratio and reinforcing particles had direct effects on the corrosion behavior, so that with the presence of HA particles and applying the higher extrusion ratio, the corrosion resistance of the samples was improved.