Effects of alloying and extrusion temperatures on the microstructure, mechanical properties, and biodegradability of zinc alloys

Abstract

Zinc-based alloys are emerging as potential alternatives to Mg and Fe-based biodegradable alloys. However, zinc's relatively poor mechanical properties must be enhanced to make it suitable for biodegradable implant applications. Therefore, efforts are being made to improve the mechanical properties of zinc through alloying and deformation processing. This study focuses on the effect of adding manganese (Mn) and copper (Cu) to zinc, as well as the influence of extrusion temperature, on its mechanical properties. The as-cast Zn, Zn-0.8Mn, and Zn-0.8Mn-0.8Cu (wt.%) alloys were cast and extruded at varying temperatures of 200, 250, and 300 °C. The hardness, elastic modulus, tensile strength, and compressive strength of the extruded alloys were compared to those of pure zinc. The elastic modulus of the as-cast Zn and its alloys was approximately 86 GPa, which increased to 125 GPa after hot extrusion. This notable increase in modulus is attributed to the texture developed during the hot extrusion process. Alloying addition, perse increased the hardness of zinc by 44–61 %. At the same time, samples subjected to hot extrusion were observed to have less hardness than the as-cast counterparts. The influence of extrusion temperature on hardness was insignificant. Adding Mn and Cu improved the compressive yield strength of zinc (43–145 MPa, i.e. 239 %). The zinc's compressive yield strength increased by 258 % after hot extrusion, but it is just 28–47 % for the alloys. Whereas tensile strength of zinc has been increased by 125 % through alloying and hot extrusion. Amongst the various alloys tested, the binary alloy Zn-0.8Mn phenomenally exhibited 48–74 % of ductility after the hot-extrusion. The degradation rate in simulated body fluid was evaluated through electrochemical tests. The hot-extruded materials exhibited higher corrosion rates (0.141–0.681 mm/year) than the as-cast counterparts (0.036–0.325 mm/year).