Infiltration and reduction-driven interfacial bonding of molten magnesium in 3D-printed porous zirconia scaffolds

The design of multifunctional ceramic–metal composites is essential for advancing high-performance materials in both structural and biomedical fields. Here, we report for the first time the infiltration, magnesiothermic reduction of zirconia, and interfacial bond formation within 3D-printed porous scaffolds exposed to molten magnesium. This redox-driven transformation converts stoichiometric ZrO2 into oxygen-deficient black zirconia (ZrO2−x), creating oxygen vacancies. Although sessile drop tests revealed macroscopically poor wetting, permanent Mg–ZrO2−x bonds were established through interfacial oxygen transfer, underscoring the decisive role of oxygen management in joining otherwise non-wetting systems. Infiltration of molten Mg into porous scaffolds occurred only under force-assisted injection, demonstrating that external pressure is required to achieve effective penetration in such architectures. Metallographic analysis further revealed a discontinuous distribution of Mg, dictated by pore geometry and interfacial reactions. These findings identify oxygen vacancy formation and pressure-assisted infiltration as key parameters for Mg/ZrO2 integration and provide a framework for designing bioinspired interpenetrating composites where chemical reactivity complements mechanical infiltration.