Extrusion–hot rolling assisted microstructure refinement and corrosion control in Mg alloy micro-tubes for vascular stents

• ZM21 micro-tubes for vascular stent cutting were fabricated via hot extrusion followed by single-pass hot rolling, achieving a length >1000 mm, an outer diameter of 2.22 mm, and a wall thickness of 220 μm. • Recrystallization during hot rolling refined grains from 8.19 to 3.52 μm and improved UTS and ductility (276.87 ± 5.00→290.57 ± 2.68 MPa; 10.97% ± 1.21%→17.52% ± 1.45%). Concurrently, the emergence of a strong {0001}//RD basal texture, in concert with grain refinement, markedly improved the corrosion resistance of the microtubes. • Stents manufactured from the hot-rolled micro-tubes achieve a favorable balance between radial support force and controllable degradation rate. These outcomes provide a reproducible manufacturing strategy and a practical path to industrialization for biodegradable Mg stents featuring miniaturization, thinner struts, and a low system profile. Magnesium (Mg) alloys offer unique advantages for vascular stents due to their inherent biocompatibility and biodegradability. However, their inadequate formability and intrinsic corrosion susceptibility greatly restrict the manufacturing of precision micro-tubes and their application in medicine. This study introduces a combined hot extrusion–hot rolling technique for the fabrication of Mg-Zn-Mn (ZM21) alloy micro-tubes, achieving both grain refinement and performance enhancement. Optimized molds enabled the production of ultrafine tube billets (length > 950 mm, outer diameter 2.30 mm, wall thickness 0.23 mm). A single hot-rolling yielded micro-tubes with an outer diameter of 2.22 mm and a wall thickness of 0.22 mm, while refining the grain size from 8.19to 3.52 μm. Correspondingly, the tensile strength and elongation increased from 276.87 ± 5.00 MPa and 10.97% ± 1.21% in machined tubes to 290.57 ± 2.68 MPa and 17.52% ± 1.45% in rolled tubes, respectively. The corrosion resistance was greatly improved by the {0001}//rolling direction (RD) basal orientation that was induced by texture control during rolling. In vitro evaluation demonstrated enhanced radial support after expansion for stents fabricated from the rolled micro-tubes, and improved corrosion resistance in SBF solution. By integrating grain refinement and texture control within a streamlined processing route, this study establishes a robust, reproducible, and readily scalable approach to produce biodegradable Mg alloy micro-tubes with high mechanical reliability and corrosion resistance.