Hard-phase intensification by SiO2 nanoparticles for dislocation-mediated Mg supersaturation and tunable corrosion in Fe–Mg alloys

The development of Fe-based biodegradable implants is constrained by the inherently slow degradation rate. One promising approach to accelerate degradation is alloying with Mg to enhanced corrosion susceptibility via forming Mg-containing solid solutions, but the inherent immiscibility between Fe and Mg limit achievable supersaturation. In this work, SiO 2 nanoparticles were introduced into Fe-Mg composite powders during mechanical alloying (MA), followed by laser powder bed fusion fabrication of implants. Results indicate that SiO 2 acts as a hard-phase intensifier to enhance alloying efficacy through intensified energy transmission and dissipation. This process induces severe plastic deformation, promoting dislocation-mediated lattice distortion within the Fe matrix and thereby extending metastable Mg supersaturation beyond conventional MA limitations. The resultant supersaturated solid solution induces a cathodic shift in the electrode potential, increasing the electrochemical driving force for corrosion. Furthermore, SiO 2 nanoparticles exhibit hydroxyl-competitive adsorption at the metal-electrolyte interface, disrupting passivation by forming structurally defective Fe(OH) 3 /SiO 2 hybrid composites. This surface reconstruction mechanism reduces the protective capacity of the corrosion products, and enables sustained degradation kinetics with the corrosion rate maintained at 0.25 mm/year over 28 days.