Potential of biodegradable Zn alloys with fine grains for orthopedic and antibacterial applications

Abstract

Zinc (Zn) alloys with high elongation have attracted significant attention in biomedical applications. These alloys possess fine-grained microstructures that greatly influence their corrosion behavior and biocompatibility. In this study, a minor addition of Cu decreased the average grain size from 17.36 μm in pure Zn to 2.15 μm in the Zn-0.4Cu alloy after equal channel angular pressing (ECAP). Results demonstrated that grain refinement enhanced elongation to 200% by altering the deformation mechanism. The deformation mode of pure Zn was dominated by twin-induced dynamic recrystallization (T-DRX), while that of the Zn-0.4Cu alloy was characterized by dislocation slip and grain boundary sliding. Furthermore, grain refinement led to a decrease in corrosion rate from 270.72 ± 9.76 μm per year to 186.34 ± 8.63 μm per year, which was attributed to a shift in corrosion mode from pitting corrosion to grain boundary corrosion. The occurrence of grain boundary corrosion was due to Cu enrichment near the grain boundaries, which accelerated corrosion via galvanic effects. Both pure Zn and Zn–Cu alloys demonstrated excellent biocompatibility with endothelial cells and bone marrow stem cells. The reduced concentration of Zn²⁺ ions promoted the osteogenic properties of Zn-0.4Cu alloys via grain refinement. Moreover, the release of Cu²⁺ ions improved the antibacterial properties. These findings offer valuable insights into the impact of grain refinement on the mechanical properties and corrosion behavior of biodegradable Zn alloys.