• • Grain size reduction from 181.8 μm to 50 nm via high-speed rolling and Li addition yields a yield strength of 382.2 MPa and ultimate tensile strength of 433.3 MPa in the Zn−3Cu−0.2Sr−0.4Li alloy, enabling load-bearing biodegradable implants that can compete with permanent Ti and Fe devices while avoiding revision surgery.
• • The 0.4Li alloy exhibits a 173% increase in yield strength and a 591% increase in elongation compared to the as-cast Li-free alloy, with elongation reaching 15.2%, which addresses the inherent brittleness of as-cast Zn alloys and provides sufficient ductility for orthopedic fixation devices during bone healing.
• • Nanocrystalline strengthening contributes 70.4% to the total yield strength of the rolled Zn−3Cu−0.2Sr−0.4Li alloy, establishing grain boundary strengthening as the primary strengthening mechanism and validating HSR as a scalable thermomechanical route for bulk nanocrystalline Zn alloys.
• • The fracture mode transitions from brittle in the as-cast 0.4Li alloy to ductile after rolling, indicating that the refined microstructure with dispersed ε, β, and SrZn13 phases effectively blunts crack propagation, which is critical for clinical reliability under cyclic loading.