Fabrication of Mg alloy tubes for biodegradable stent application

• A fixed mandrel drawing method is proposed to fabricate thin-walled Mg alloy stent tubes.
• The microstructure, dimensional accuracy, and mechanical strength of the fabricated tubes are examined.
• Processing optimization enables high dimensional accuracy of Mg stent tube.
• The hcp orientation of Mg affects the corrosion property.
• The hcp orientation of Mg stent tube can be controlled by thermo-mechanical treatment.

Though Mg alloys are promising candidates for biodegradable stents, it is very difficult to fabricate stent tubes with high dimensional accuracy using Mg alloys because of their low deformability. This study aimed to develop thin-walled, high-quality Mg alloy tubes with good performance in stent applications. Cold drawing with a fixed mandrel was carried out for extruded Mg-0.8%Ca and AZ61 alloy tubes using optimized drawing parameters and lubrication, and stent tubes with 1.5–1.8 mm outer diameter and 150 μm thickness were fabricated. A dimensional evaluation showed that the tube dimensional errors were within 0.02–2.5%. Also, an immersion test of pure Mg with different crystal orientations showed that the crystal orientation affected the corrosion properties, results that are the same with other Mg alloys. The crystal orientation of the stent tube could be controlled by changing the deformation amount and direction in the drawing, showing that it is possible to further improve the biodegradability of stents by approaching their fabrication from a processing aspect.