Structure effects on mechanical behavior and permeability of Zn–3Mg scaffolds with gradient triply periodic minimal surface

Additive manufacturing (AM) offers new opportunities for developing biodegradable bone substitutes with personalized structures and tunable properties. Zn–Mg alloys have shown great potential in bone repair due to their suitable degradation rate, good biocompatibility, and favorable mechanical properties. However, most existing studies focus on uniform structures, and systematic research on the mechanical compatibility and permeability of Zn–3Mg alloys with gradient triply periodic minimal surface (TPMS) structures is still lacking. In this study, Zn–3Mg scaffolds with different gradient designs (gyroid, primitive, and diamond) were fabricated using selective laser melting (SLM). Microstructural analysis revealed that rapid solidification significantly refined the grains and promoted a uniform distribution of α-Zn/Mg 2 Zn 11 eutectic and MgZn 2 intermetallic phases, while stronger lattice distortion and higher brittleness were observed along the vertical direction. The gradient design notably optimized pore distribution and improved mechanical behavior, resulting in a progressive layer-by-layer collapse mode under compression while avoiding stress shielding effects. Permeability analysis showed that gyroid scaffolds exhibited nearly isotropic permeability, whereas primitive and diamond scaffolds had higher axial permeability, with overall permeability decreasing as the unit cell size decreased. Cell experiments further confirmed the good biocompatibility of the scaffolds. This work highlights the potential of periodic gradient structures in Zn–3Mg alloys and provides a valuable reference for the functional design of biodegradable metal scaffolds for clinical bone defect repair.