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 alpha-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 (iCorr) of 10 mu A/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.