Synergistic enhancement of microstructure, mechanical properties, degradation resistance, and cytocompatibility in AZ31 Mg alloy via minor Er alloying for biodegradable implants

The clinical application of biodegradable Mg alloys is mainly limited by their overly rapid degradation and associated biocompatibility concerns. This work demonstrates that minor erbium (Er, 0.5 wt.%) alloying in AZ31 Mg alloy effectively addresses these challenges by fundamentally modifying degradation behavior and biological interactions. The resultant structural refinement and the formation of thermally stable Al 3 Er precipitates not only enhance mechanical strength, with ultimate tensile strength (UTS) and yield strength (YS) increasing by ∼7% and ∼14%, respectively, but also significantly reduce the corrosion rate in simulated body fluid (SBF), through the formation of a stable, protective Er 2 O 3 -rich surface film that incorporates bioactive Ca-P compounds. This controlled degradation kinetics minimizes local pH elevation and burst ion release, particularly reducing the emission of potentially neurotoxic Al ions by trapping them within stable Al 3 Er phase. The Er 2 O 3 -rich surface film, incorporating bioactive bone-like Ca–P compounds, further enhances biological performance. Consequently, the AZ31-0.5Er alloy exhibits superior cytocompatibility, evidenced by significantly enhanced MC3T3-E1 pre-osteoblast viability, adhesion, and cytoskeletal organization. The synergistic improvement in biosafety and bioactivity, achieved through interface stabilization and regulated ion release, establishes this Er-modified alloy as a highly promising candidate for load-bearing biodegradable implants.