Study on the Fabrication and Properties of Magnesium Alloy Microtubes for Vascular Stent

Abstract:

Magnesium alloys, as a new type of biodegradable medical metal material, have a promising application in the field of vascular stents. However, the poor deformability of Mg alloys due to hexagonal close-packed (hcp) structure makes it difficult to fabricate their thin tube. In this study, the micro-tubes of Mg-4Zn-0.2Mn-0.2Ca alloy, a new type of degradable magnesium alloy, with 3.1～3.6 mm in outer diameter and 0.25～0.4 mm in thickness were prepared by hot extrusion-drawing composite process. The microstructure evolution and mechanical properties of the one with 3.6 mm in outer diameter, 0.4 mm in thickness showed that the crystal slip, twins and recrystallization occurred during the plastic deformation of the tubes, and the work hardening was significant. This drawn tube exhibited a tensile strength of 427.3 MPa, yield strength of 383.4 MPa, and elongation of 5.2%. After annealing at 300℃ for 30 min, the microstructure became uniform and the elongation increased to 18.0%, which is conducive to the fabrication of vascular stents.

Key words:Mg-Zn-Mn-Ca alloy; extrusion; drawing; microstructure evolution; mechanical properties