Tensile Properties and Corrosion Behavior of Biodegradable In Situ Formed Mg–Si Alloys and Composites

Tensile properties and in vitro corrosion behavior of biodegradable Mg– x Si alloys and composites in the simulated body fluid (SBF) solution were investigated. Besides pure magnesium, the hypoeutectic ( x = 0.1 and 0.5 wt%), near-eutectic ( x = 1.2 wt%), and hypereutectic ( x = 4 wt%) compositions were considered. The Si addition in the hypoeutectic range resulted in the grain refinement of as-cast ingots, formation of α–Mg/Mg 2 Si eutectic structure, and improvement of strength-ductility synergy. However, higher Si additions (1.2 and 4 wt%) led to poor tensile properties. Accordingly, the Mg–0.1Si and Mg–0.5Si alloys showed the best combination of tensile properties. The hot extrusion process resulted in a significant grain refinement induced by the dynamic recrystallization (DRX) and fragmentation of particles due to deformation, which led to a notable improvement of comprehensive tensile properties. For instance, the lean Mg–0.5Si alloy exhibited the highest tensile toughness value of 37.3 MJ/m 3 , which is much larger than the value of 5.2 MJ/m 3 for the as-cast pure Mg. The extruded Mg–0.1Si sample showed the lowest corrosion current density ( i Corr ) of 10 μA/cm 2 in the SBF solution compared to other samples, which was ascribed to the fine grain size and formation of appropriate protective film with a high Ca/P ratio. However, higher Si additions resulted in the deterioration of corrosion resistance due to the increased amount of Mg 2 Si phase. Accordingly, the Mg–0.1Si alloy was considered as a proper candidate for providing the best combination of tensile properties and corrosion resistance in biomedical implant applications.