Mechanical, wear, and biocorrosion behavior of biodegradable Mg–3Zn–3Sn–xLi alloys: The synergistic role of Li addition and thermo-mechanical processing

This study assessed the influence of thermomechanical processing techniques on the microstructural evolution, mechanical integrity, and biodegradation behavior of Mg–3Zn–3Sn (ZT33) and Mg–3Zn–3Sn–3Li (ZTL333) alloys. Rietveld refinement indicated that the addition of lithium (Li) changed the lattice parameters. In contrast, hot extrusion caused complete dynamic recrystallization (DRX), changing the coarse dendritic structures into a refined, uniform microstructure (18.4 μm for E-ZTL333). The extruded ZTL333 alloy exhibited the standards for cortical bone, with a hardness of 68.52 HV and a Compressive yield strength of 417.26 MPa. Electrochemical and immersion studies in Dulbecco’s Modified Eagle Medium (DMEM) revealed that microstructural uniformity and Li-modulated surface alkalinity are the most important factors for long-term stability. These factors cancel out the natural reactivity of Li and encourage the promote the deposition of Ca-P-rich bioactive minerals with a Ca/P ratio close to that of hydroxyapatite (HA). These results indicate that the processing technique is the most important factor in matching the mechanical strength with controlled degradation. This makes E-ZTL333 a promising candidate for biodegradable orthopedic implants.