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–xSi 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/Mg₂Si 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/m³, which is much larger than the value of 5.2 MJ/m³ for the as-cast pure Mg. The extruded Mg–0.1Si sample showed the lowest corrosion current density (i_Corr) of 10 μA/cm² 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 Mg₂Si 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.