The Forming Processes And Structure Property Of WE43 Magnesium Alloy Stent Tube With High Precision

Magnesium alloy stent is a new type of biodegradable stents, it has been widely concerned that the research and development on magnesium alloy stent. But it is difficult to be formed for its low plasticity at room temperature. It is low in precision that the stent tube prepared by traditional method, so it often cannot meet the requirements of stents usage. It has been researched that the heart stent tube(WE43 magnesium alloy) forming technology in this paper, a set of perfect forming process was formulated, and it could be produced that the heart stent tube with high dimensional accuracy by this forming process. First, solution treatment was conducted on those extruded tubes, which was beneficial for improving their plasticity. Then, the tube drawing and rolling process was simulated to formulate the reasonable tube forming scheme. Finally, it was successfully produced that the heart stent tube(WE43 magnesium alloy) with high precision by drawing-rolling intersecting process. The tube size is 4mm in diameter and 0.25mm in wall thickness.The original size of extrusion die has been optimized, the external diameter of extrusion cup is reduced to 50mm, the modular angle of extrusion cup is optimized to 60°, and the working tape length is optimized to 2mm. Thus the extrusion ratio is reduced, and the success rate of tube extrusion is improved.In the process of tube solid solution treatment, something has been founded. With the increase of solution temperature and solution time, the second phase in the grain boundary is gradually reduced, and the tube plasticity is gradually increased. When the solid solution treatment is 525℃×12h, its plasticity is best.Based on the simulation to the tube drawing process, it has been founded that the drawing force showed a rising trend with the increase of drawing speed under the same deformation. When the drawing speed is 0.2mm/s, the force on the tube is the most evenly during the drawing process.Based on the simulation to the tube rolling process, it has been founded that the tube deformation is uniform when the deformation is less than 20%, when it is more than 20%, the tube will be fractured in the process of rolling.According to the simulation results, an appropriate forming scheme has been formulated: sink drawing-rolling-drawing with spindle-rolling. At last, the tubes size precision has met the requirements of preparing the stents.