Multiscale heterostructured Mg-2Zn alloy for biodegradable implants: Coordinated strength-ductility, moderate...

High-strength lean-alloy magnesium (Mg) has attracted extensive attention for orthopedic and vascular stent implants owing to its favorable biodegradability and biocompatibility. However, while retaining the chemical composition of specimens and ensuring high biosafety, the major challenge is to overcome the strength-ductility trade-off and achieve uniform degradation behavior. In this study, a lean Mg-2 wt% Zn alloy with balanced strength and ductility was fabricated via hot working. The alloy possessed a bimodal heterogeneous structure composed of fine-grained regions containing nanograins and nanotwins, as well as coarse-grained regions. It attained an ultimate tensile strength of approximately 350 MPa with an elongation of 13%. This heterostructured Mg-2Zn alloy exhibits better performance compared with the commercial rare-earth-containing WE43 alloy. Moreover, it demonstrated slow degradation rates (0.07 mm·year^-1in vitro and 0.11 mm·year^-1in vivo) driven by multi-phase interface effects. Furthermore, the heterostructured Mg-2Zn alloy exhibited antibacterial activity in vitro and a relatively mild peri-implant inflammatory response in vivo. This study differs from conventional rare-earth alloy strengthening strategies, clarifies the formation and regulation mechanisms of heterostructures, and provides theoretical and technical support for the clinical translation of high-performance biodegradable Mg alloys. STATEMENT OF SIGNIFICANCE: To address the bottleneck of balancing mechanical performance and biocompatibility in rare-earth-free magnesium (Mg) alloys for biodegradable temporary implants, this study employed a multi-pass hot-rolling process with an optimized final rolling temperature to produce the lean-alloyed Mg-2Zn heterostructured alloy. The alloy achieved a reasonable combination of tensile strength (349 MPa) and elongation (13%), mitigating the common strength-ductility trade-off observed in Mg-2Zn alloys. Metabolomic analysis showed that metal ions slowly released during alloy degradation could regulate biological energy metabolism, endowing the material with antibacterial activity in vitro and a relatively mild peri-implant inflammatory response in vivo. This study clarified the mechanisms associated with heterostructure formation, strength-ductility synergistic strengthening, slow degradation, and biological metabolic regulation. It also provided experimental support for the research and development of high-performance rare-earth-free Mg-based biomaterials.