Developing 400 MPa grade biodegradable Zn alloys with superior osteogenic and antibacterial performance

Abstract

Abstract Biodegradable zinc (Zn) has emerged as a promising orthopedic implant material, capable of supporting bone repair while gradually resorbing in the body. Yet, its relatively low strength has restricted its use in high load-bearing scenarios. The addition of lithium (Li) improves mechanical strengths of Zn alloys, of which are comparable to that of pure Ti. Here, we present a Zn-0.8Li alloy system enhanced through alloying and equal channel angular pressing (ECAP). By tuning the processing temperature, the alloys attained superior mechanical performance, with tensile strength reaching 434 MPa and elongation of 65% at 200 °C. The dominant strengthening mechanisms were identified as grain boundary strengthening and dislocation strengthening. Corrosion assessment revealed a stable degradation rate of ~ 5.5 μm/year after 30 days of immersion, with localized attack at second phases and grain boundary corrosion in ultrafine-grained microstructures (T-150 and T-200 samples), whereas a fine-grained microstructure (T-300 sample) exhibited suppressed boundary corrosion. In vitro studies confirmed excellent cytocompatibility and osteogenic potential of the ECAP-treated Zn-0.8Li alloys compared with bioinert Ti. Furthermore, antibacterial tests demonstrated inhibition rates exceeding 90% against E. coli colonies.