Electrodeposited Heterostructured Fe-Zn Alloy Microtubes for Vascular Stents: Achieving Enhanced Strength, Ductility, and Uniform Degradation

To synergistically enhance the strength-ductility trade‑off and achieve uniform degradation in Fe-Zn alloys, heterostructured alloy microtubes were fabricated via layer‑by‑layer electrodeposition on a rotating soluble aluminum mandrel. Microstructural characterization revealed a columnar‑layered architecture with coherent interfacial bonding after annealing, free of delamination or defects. The heterostructured sample containing ten alternating soft layers (FZ10) exhibited an ultimate tensile strength of approximately 605 MPa and an elongation of about 17.3%, both superior to those of the single-layer alloy. The loading-unloading-reloading (LUR) experiments demonstrated pronounced hetero-deformation induced (HDI) strengthening and HDI strain-hardening effects, indicating the critical role of interfacial constraints in deformation coordination. Electrochemical and simulated body fluid (SBF) immersion tests showed that the heterostructure promoted faster and more uniform corrosion, with an average degradation rate of approximately 0.135 mm·y^{- 1} after 56 days, suppressing localized pitting. XPS and FTIR analyses identified the corrosion products as Fe/Zn oxides and Ca-P compounds, forming a bilayer degradation film with a dense inner layer and a loose outer layer. Additionally, heterostructured Fe-Zn alloy microtubes exhibited favorable cytocompatibility. These heterostructured microtubes integrate high strength, ductility, and controlled and uniform degradability, making them promising candidates for further development as biodegradable vascular stent materials.