Enhancement in mechanical and corrosion resistance properties of a biodegradable Zn-Fe alloy through second phase refinement

Biodegradable Zn alloys containing Fe suffer from a common problem that FeZn13 second phase particles are coarse. This problem roots thermodynamically from the negligible solid solubility of Fe in Zn and priority of FeZn13 solidification over Zn. In this paper, bottom circulating water-cooled casting method is successfully developed to significantly refine FeZn13 particles in Zn-0.3Fe alloy, owing to its cooling speed about 8 times of that of conventional casting. The second phase refinement alleviates brittleness of the alloy, increases the ultimate tensile strength by about 62%, and decreases electrochemical corrosion rate (CR) by about 19%, but immersion CR by only about 4% due to barrier effect of corrosion products. Viability of human umbilical vein endothelial cells maintains at a high level over 95% in 25-100% extracts. A great potential is shown for improving comprehensive properties of biodegradable Zn alloys without changing its chemical compositions through such a physical method.