Processing and properties of magnesium alloy micro-tubes for biodegradable vascular stents

Magnesium alloys are considered to be one of the most promising stent materials due to their good biological compatibility and biodegradable properties. However, the poor workability at room temperature restricts the processing of high-precision micro-tubes for the application as stent materials. In this study, Mg-Zn-Y-Nd alloy tube blank was firstly produced through hot extrusion. By multi-pass cold drawing combining with interpass annealing, the extruded tube blank can be processed into high-precision micro-tube with an outer diameter of about 2.0 mm and a wall thickness of about 0.15 mm. The drawn micro-tube after annealing exhibits improved mechanical properties with an ultimate tensile strength of about 298 MPa and a large breaking elongation of up to 20%. Meanwhile, the micro-tube shows good corrosion resistance with a trend of uniform corrosion in simulated body fluid solution. The investigation revealed that a significant improvement in the mechanical properties is mainly attributed to grain refinement and texture weaken, while the good biodegradable properties is related with the low density of crystallographic defects as well as fine and homogeneous microstructure. As a result, the successful processing of magnesium alloy micro-tube provides the precursor for laser engraving stents.