Ultrahigh strength and uniform corrosion in Zn-Li alloys through ultrahigh pressure supersaturated solid solution treatment for biodegradable orthopedic applications

Zn-Li alloys are considered promising candidate materials for biodegradable orthopedic implant applications due to their high mechanical performance and good biocompatibility. However, the presence of a large number of second-phase particles in this class of Zn alloys can lead to severe localized degradation due to micro-galvanic corrosion, which is detrimental to the mechanical integrity of the alloys during tissue healing in the human body. In this study, we report ultrahigh strength, uniform corrosion, good cytocompatibility, and effective antibacterial ability in Zn-xLi (x = 0.3, 0.5, 0.7; wt%) alloys achieved through supersaturated solid solution treatment (SSST) at 375 °C under ultrahigh pressure of 3 GPa. A high concentration of β-LiZn₄ phases coexisted with the -Zn matrix in the as-cast Zn-xLi alloys, whereas almost all the Li dissolved into the -Zn matrix of SSST counterparts. The yield strength was 437 MPa for SSST Zn-0.3Li, 592 MPa for SSST Zn-0.5Li, and 686 MPa for SSST Zn-0.7Li. The SSST Zn-Li alloys showed uniform degradation with remarkably reduced degradation rates compared to their as-cast counterparts. The 25% concentration extracts of the Zn-xLi alloys demonstrated no cytotoxicity toward MC3T3-E1 cells, and the alloys exhibited effective antibacterial ability against methicillin-resistant staphylococcus aureus.