Effects of extrusion temperature on microstructure, mechanical properties and in vitro degradation behavior of biodegradable Zn-3Cu-0.5Fe alloy.

Abstract

Zn-based alloys as biodegradable materials for cardiovascular stents have drawn more and more attention in recent years. However, the hot plastic deformation of Zn-based alloys does not get enough attention. In this study, Zn-3Cu-0.5Fe alloy was prepared and then hot extruded at 140, 180, 220 and 260 °C. Effects of extrusion temperature on the microstructure, mechanical properties and degradation behavior were investigated. Nano-scaled particles precipitated during extrusion and the quantity decreased with the increasing of extrusion temperature. As the extrusion temperature increased from 140 to 260 °C, the grain size increased from 1.15 to 4.38 μm, the yield strength and ultimate tensile strength increased from 203 ± 3.23 and 221 ± 1.56 MPa to 269 ± 2.65 and 302 ± 8.01 MPa, increased by 32.5% and 45%, while the degradation rate was decreased gradually from 62.8 ± 0.72 μm/year to 49.9 ± 3.35 μm/year, decreased by 20.5%. In addition, the degradation behavior changes from a relatively uniform degradation mode to a localized degradation mode with the increase of the grain size. Dislocation gliding is replaced by grain-boundary movement and dynamic recrystallization (DRX) in the room temperature tensile deformation process. Lower extrusion temperature is beneficial for higher elongation and degradation rate as well as relatively uniform degradation mode, which is better suitable for the clinical application of cardiovascular stents.