Enhancing biodegradable Mg-3Sn alloy via yttrium addition and heat treatment: Microstructure, mechanical performance, corrosion resistance, and biocompatibility

• Addition of 1 wt. % yttrium to Mg–3Sn alloy forms thermally stable intermetallic phases (Sn3Y5, MgSnY), enhancing microstructural stability. • Optimized solution treatment followed by aging refine precipitates, significantly improving mechanical strength (peak shear strength of 129 MPa) and hardness. • Yttrium addition markedly reduces corrosion rates by mitigating micro-galvanic effects and promoting protective Sn- and Y-rich surface films. • Both Mg–3Sn and Mg–3Sn–1Y alloys exhibit excellent biocompatibility with adipose-derived stem cells, showing no cytotoxicity and improved cell viability. • Alloys demonstrate intrinsic antibacterial properties, with aged samples showing stronger inhibition of bacterial growth, reducing implant infection risk. Although magnesium alloys are attractive for temporary implant applications due to their favorable biocompatibility and mechanical properties, their rapid in vivo degradation remains a significant limitation. This study investigates the effect of adding 1 wt.% yttrium on the microstructure, mechanical properties, corrosion resistance, and biocompatibility of as-cast Mg–3Sn alloy, while employing solution treatment and artificial aging to optimize these properties. In the as-cast condition, Mg–3Sn primarily contained Mg 2 Sn precipitates, whereas the Mg–3Sn–1Y alloy exhibited a complex mixture of Mg 2 Sn, MgSnY, and Sn 3 Y 5 phases. Solution treatment fully dissolved Mg 2 Sn precipitates in both alloys and partially dissolved yttrium-containing phases in Mg–3Sn–1Y. Subsequent aging led to the formation of ultrafine Mg 2 Sn and Mg 24 Y 5 precipitates. Mechanical testing revealed that the Mg–3Sn–1Y alloy consistently outperformed the binary Mg–3Sn alloy across all conditions, achieving a peak ultimate shear strength of 128.3 MPa in the age-hardened state. Electrochemical measurements and hydrogen evolution tests demonstrated that 1 wt.% yttrium addition significantly reduced the corrosion rate in all tested conditions, with the lowest rate of 4.19 mm/year observed in the solution-treated Mg–3Sn–1Y alloy. Furthermore, in vitro biocompatibility assays using adipose-derived stem cells showed enhanced cellular activity for both alloys, with the Mg–3Sn–1Y alloy exhibiting superior performance compared to the inert control group. These findings highlight the beneficial role of 1 wt.% yttrium in improving the structural, corrosion, and biological properties of Mg–3Sn alloy for potential biomedical implant applications.