Additive Manufacturing of Fe‐AZ31 Immiscible Bimetallic Composites for Degradable Implants

Revision surgeries for implantable metal devices/plates are relatively common, often due to palpability/prominence, infection, or complications arising from stress shielding. The potential need for surgical removal of metal fixation plates could be obviated by using degradable metal implants that dissolve after the bone has healed. Iron is a promising candidate for a degradable metal, but its slow degradation rate limits its effectiveness. This study investigates the microstructural and degradation characteristics of a novel Fe‐AZ31 composite synthesized via directed energy deposition (DED). Immersion test on Fe‐AZ31 samples demonstrates improved degradation kinetics, with the composite degrading at ≈1.2 mm year −1 compared to ≈0.1 mm year −1 for pure iron. This enhanced degradation rate is attributed to various mechanisms, including Mg acting as sacrificial sites for corrosion, which leaves pits in iron, and Mg partially dissolving in Fe, potentially lowering its electrochemical potential. Furthermore, contributions from the additive manufacturing process like surface roughness and fine microstructure could also enhance degradation kinetics. Importantly, the composite exhibits a more controlled pH change with respect to AZ31 magnesium‐alloy, suggesting less release of hydroxyl ions, and consequently reduces hydrogen evolution. This work lays the foundation for further exploration of Fe‐AZ31 composite, opening up new possibilities for the development of advanced degradable implants.