Effect of Zn on corrosion behaviour of biodegradable Mg-Zn-Mn alloys evaluated by FE prediction and in-vitro testing

Mg-Zn-Mn (ZM) alloy shows great potential in biomedical applications due to its biocompatibility and bio-essential element composition, as well as its favourable mechanical and degradation properties. This paper aims to explore the effect of Zn on corrosion behaviour of ZM alloys via finite element (FE) prediction and in-vitro testing. Microstructure analysis showed that Zn had the grain refinement effect, and the second phase of Mg-Zn between grains increased with the increase of Zn content, which improved the mechanical properties of the alloy significantly at the cost of acceptable reduction in plasticity. After a continuum damage mechanics (CDM)-based degradation model was applied to the FE package, the corrosion process of the ZM alloys was predicted. The results indicated that the grain boundary had poor corrosion resistance while the second phase facilitated delaying corrosion expansion. Furthermore, in-vitro tests were carried out and consistent results were obtained, i.e., the grain refinement made the entire corrosion process more uniform and severe corrosion in local areas was avoided, and the intergranular second phase was beneficial to delay the corrosion process. This study suggested that Mg-Zn-Mn alloy has satisfactory mechanical strength and controllable corrosion rate, which should be a promising candidate for future biomedical applications.