Superior strength-ductility synergy in heterostructured zinc alloy implants fabricated via laser powder bed fusion

Abstract Zinc and its alloys are promising biodegradable materials for orthopedic implants, but simultaneously enhancing strength and ductility remains challenging. In this study, laser powder bed fusion technology was employed to fabricate zinc-copper (Zn–Cu) alloy implants. Within the optimized processing window, increasing the laser energy density elevated the melt pool temperature and provided sufficient thermodynamic conditions for grain growth, whereas decreasing the energy density accelerated cooling and suppressed grain coarsening. By grouping multiple layers and alternately applying high and low energy densities between groups, a heterostructure with alternating coarse- and fine-grained layers was constructed. These heterostructured Zn–Cu alloys exhibited an ultimate tensile strength of (245.6 ± 8.7) MPa and a ductility of (12.7 ± 0.9)%, demonstrating a remarkable strength-ductility synergy among LPBF-processed Zn-based alloys. Mechanical analysis revealed that heterodeformation-induced stress, interlayer dislocations, and the inhibition of strain localization collectively contributed to the superior mechanical performance. Additionally, the heterostructured Zn–Cu alloys exhibited typical gradient degradation characteristics and outstanding osteogenic activity, highlighting their potential for load-bearing biodegradable orthopedic applications. This work establishes a process-microstructure-property paradigm for LPBF of Zn alloys and offers a generalizable strategy for designing high-performance biodegradable metal implants.