Influence of magnesium addition on microstructural and mechanical stability of hydrostatically extruded biodegradable zinc alloys

Biomaterials must satisfy strict requirements regarding high mechanical properties, proper corrosion rate and biocompatibility impose on medical implants. Pure and low alloyed zinc is an excellent material being considered for applications as biodegradable devices like coronary stent or orthopedic implants due to its optimal corrosion rate. However, it possesses low mechanical properties and can recrystallize in the room temperature. To solve the issues alloying with magnesium and plastic deformation by hydrostatic extrusion was applied. Significant improvement was attributed to refine the microstructure. However, the thermal stability of this microstructure has not been investigated so far. Thus, in this research, the effect of magnesium addition on the mechanical and microstructural stability during heating was studied for alloys with 0.6 and 1.2 wt. % of magnesium subjected to hot and hydrostatic extrusion. To fully understand the obtained results, they were compared with pure zinc as a reference material. It was shown that the microstructure after plastic deformation strongly affect the material's behavior during the heating. Moreover, the higher amount of alloying additive can inhibit static recrystallization processes. Additionally, the influence of the density of low angle grain boundaries on the obtained compressive yield strength values was highlighted.