Microstructure and texture evolution of fine-grained Mg-Zn-Y-Nd alloy micro-tubes for biodegradable vascular stents processed by hot extrusion and rapid cooling
Kaikai Guo, Mengyao Liu, Jianfeng Wang, Yufeng Sun, Weiqing Li, Shijie Zhu, Liguo Wang, Shaokang Guan
Abstract
Magnesium alloys have narrow available slip result from close-packed hexagonal structure that limit their processing properties. In the recent work, the Mg-2Zn-0.46Y-0.5Nd, as materials for degradable stents, was applied to produce as-extruded micro-tube with an outer diameter of 3.0 mm and a wall thickness of 0.35 mm by hot extrusion with an extrusion ratio of 105:1 at 653 K and rapid cooling. The fine microstructure of the dynamic recrystallization of as-extruded micro-tube could be preserved by rapid cooling such as water-cooled, resulting in more excellent mechanical properties relative to air-cooled micro-tube. The addition of rare earth elements Y and Nd results in continuous dynamic recrystallization dominated the dynamic recrystallization mechanism. During the hot extrusion process, the activation of the non-basal slip system, especially the pyramidal 〈c + a〉 slip, could significantly weaken the texture strength, and the as-extruded micro-tube exhibits weak “RE” texture components 〈011¯1〉∥ED and 〈1¯21¯1〉∥ED. Hence, the magnesium alloy micro-tube prepared by the rapid cooling has fine microstructure and weak texture, which is favorable for further process and governance.