血管支架用镁合金微细管制备工艺与性能研究

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

摘要:

镁合金作为新型可降解医用金属材料,在血管支架领域具有广阔的应用前景。由于镁合金晶体结构为密排六方结构,塑性变形能力差,导致镁合金微细管制备困难。本文针对作者开发的新型可降解Mg-4Zn-0.2Mn-0.2Ca镁合金,采用热挤压-拉拔复合工艺成功制备出外径3.1～3.6 mm、壁厚0.25～0.4 mm的微细管。针对外径3.6 mm,壁厚0.4 mm微细管组织演变及机械性能开展的研究结果表明：微细管材的塑性变形经过了滑移、孪生及再结晶等过程,并产生了显著的加工硬化现象；管材的抗拉强度为427.3 MPa,屈服强度为383.4 MPa,伸长率为5.2%；经300 ℃,30 min的退火处理,管材组织变得相对均匀,强度有所降低,但伸长率增加到18.0%,有利于后期支架的精密加工。

关键词:Mg-Zn-Mn-Ca镁合金;挤压;拉拔;组织演变;机械性能

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