Abstract: 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 8.19 to 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.

Key words: Magnesium alloys, Micro-tube, Rolling, Texture, Corrosion, Stent